I've used Ubuntu as at least a dual booted daily driver since 2016 and have also discussed with friends and family about what they liked and hated about it when they have used it, how they use their computer and whether they would swap. Here are some observations from that:

Hardware Issues and stability: For the most part, I've not really had to deal with hardware issues outside of trying to get NVidia graphics cards to play nice with everything else. However, I often have weird system stability issues or just plain quality of life. E.g. 2-in-1 decides randomly when put into sleep mode to flip the screen to a random orientation which I then have to go into settings to revert back. I'm used to buggy and annoying software, but for a lot of people this is a complete killer. Similarly, while I love the diverse options within Linux, having so much diversity means that troubleshooting and testing is so much more complex and you will usually have to go over multiple answers in order to solve your problem making it much harder to get into and use reliably

MS Office: This one tends to be the largest reason in my experience for people not going over to Linux. For a lot of people this is their main use for a computer and the fact that it is not available on Linux is a deal breaker. I've tried the online version and it is just not a viable alternative (nor is any cloud option). Similarly LibreOffice is a lot better than nothing, but the UI feel like it came out of the 90s, Latex is faster and easier to use than the math input, I never have been able to get referencing to work, drawing tools are lacking if they even exist at all. Opening office documents breaks all the formatting and looks awful, etc etc.

Games and other windows software: While I think value has done wonderful work in encouraging developers of games to support Linux and Proton does work quite well, you never quite know how a game will perform on Linux and if it will even work, whereas on Windows you can guarantee it has been tested and will work well. Similarly for other software: Will this work on Wine or Crossover? Maybe or maybe not but it's a bit hard to swap if you are paying large amounts for software just to find out it cannot run on Linux.

A reason to move: I think Linux will always remain fairly niche as for most people there just isn't a good enough reason to move over from Windows or Mac. These platforms already offer them everything they want in a computer in an easy to use and polished way. For most people, they really don't care that windows is constantly spying and with ads everywhere already, what is a few more ads or that the cost of a Mac and is absolutely extortionate. Moving across would require a whole bunch of troubleshooting and learning how to do just about everything all over again and that would require a really good reason to do which Linux doesn't (and possibly can't ) provide and MS and Apple haven't done anything stupid enough to offer.

Although I do use Linux (so should not respond here, I know), the reasons are probably similar to why Android vs iOS. They are different philosophies. No-one really is wrong, it is about personal fit.

Admittedly, it's been a long time since I did anything with linux, but I have done some. I'm not a developer, I don't know how to write any code. I know some DOS scripting and now some powershell. If I need to do anything slightly different with linux, it would require me to learn a whole new scripting language, and all of the documentation I've seen for anything linux seems to be written for an audience of people who already really know what they're doing in linux and just need a specific reference material.

I've had mainly Windows machines all my life, I have been forced by necessity to figure out how to do what I need on those. I imagine if I'd had linux machines since ... 1995? I would feel as comfortable with linux now. But the barrier to entry to even having a linux machine, let alone making it do what I needed it to do, back in the late 90s, early 2000s, was way higher than it was for Windows. It arguably still is.

Tried out a few times in the 90s and early 2000s and the biggest barrier was lack of support for video cards and other hardware that I needed for gaming. It was also more complex to set up at that time, and windows was both easier to work with and resolving issues was easier to figure out.

In all cases I was dual booting and after a while just stopped trying with Linux because the other option was easier, not because I disliked Linux.

Haven't tried recently because windows 10 and 11 have been rock stable for me and Windows Defender plus Firefox and ublock origin have made it safe to use windows. While I thought about giving it a go again recently, I just don't have a reason to switch when things are going to well and I don't have time anymore to just fiddle with it due to other priorities.

I do keep an eye out though in case I do a media server or something as that would be a good use case for another go.

Gaming and HFR support.

Broken bootloader.

I'm definitely a Linux novice, tried it on and off over the last decade and currently dual boot Mint on my laptop. I love Mint, it's been the easiest version of Linux by far.

Now the bad, DaVinci Resolve Studio just does not play nice. I know this is more of a Resolve problem, but still, it doesn't connect to my NAS efficiently. As an editor, this is a deal breaker. I hope it gets fixed in the future.

Second, it won't even see my Bluetooth keyboard, once again, probably something to do with the hardware, but it works on everything else, even Android. I also have weird issues with my wireless Xbox controller in that the trigger buttons don't register in games. Still trying to troubleshoot that.

I still try to use Mint as often as I can, but there always something that keeps me from switching fully.

Rocket League on steam proton. It was choppy on Mint. Ubuntu wasn't bad, but when I alt tabbed everything slowed down.

steam deck was a fucker to set up with some github alternative.

Lastly my hdmi to 5.1 reciever kept showing as an extra monitor, which couldnt be mirrored or disabled. That was enough to call it for me.