And you will be able to upgrade a desktop computer. You could at some point swap the GPU or buy another stick of RAM for $60, whereas most things are soldered in laptops nowadays. Oftentimes they even solder the RAM to move it closer to the CPU and make the laptop a bit cheaper since it now requires less mechanical brackets/parts.

Also a laptop will almost never get the same performance because it's more difficult to get all the heat out and it'll switch to a lower clockrate once all the heat builds up in that small form-factor.

But it can be worth it if you need one device that can do both gaming and be carried around. Desktop replacements are quite popular. But they come with exactly those downsides. And it may be or might not be cheaper than buying one ultrabook plus a pc that's tailored to gaming. It's always a compromise, though.

But desktop builds won't use less electricity. I use a desktop replacement gaming laptop at home, without taking it anywhere, because it consumes less power

I mean that's fine if that's your opinion. But while they may be a mistake for you, I've found them to be a great compromise and enjoyed several of them for the past 10 years.

I have a normal laptop, a ThinkPad X1 Nano, which I love. I also have a desktop with an RX 6800, but I can only use that in my office, a cramped space which has poor Internet and is in an inconvenient spot in our house.

I'm looking for something that I can keep in the living room, and set up on our living room table to play some games with friends. I've had that desktop for almost 3 years and yet I've done most of my gaming since I had it on a 2013 Alienware laptop with an upgraded MXM graphics card.

Different solutions for different people.