Phones are developed to store as much in RAM as possible. Storage is slow, and users are expected to switch between apps constantly. It's not uncommon for hundreds of apps to be loaded, including their state, at the same time. Apps that don't fit into memory are saved to storage, but the most common apps and services are kept around.

Common files are also cached in memory for performance reasons. If you don't have any RAM available, browsing files or photos would be terribly slow.

The GPU shares RAM on many devices, and that'll take a significant chunk out of your system memory. Rendering 60 frames per second on a 1440p screen isn't cheap, especially if you have ten different apps ready to render full screen at all times.

My phone has about 4½GB assigned to applications, the rest is cache. I'd say phones with less than 6GB of RAM would work, but not very smoothly.

The more RAM, the easier switching between apps becomes. Websites and apps have become huge, not only because of inefficiencies but also because of how huge the graphics they need to render have become, and the expectation that everything works with a smooth 60-90-120Hz all the time. Do you need 12GB? Hard for me to tell. I can tell that my phone's 6GB struggles when Firefox is open while Youtube is playing and I need to switch to my password manager. It'll hold out, but only just, one more app and Firefox gets unloaded. Then again, my password manager seems to be suffering from some kind of memory leak, because there's no reason it would need this much RAM.

I don't know what Macbook you have, but if someone is buying a laptop these days, I wouldn't recommend getting anything with less than 16GB of RAM or an upgrade slot. Web browsers have become operating systems of their own and buying 8GB laptops now will make your device last less than five years, at least comfortably. I would personally advocate for 32GB or more if you're planning on using your laptop for ten years, based on current trends.

Even still, many people can and do use phones the wag they did desktops ten years ago. It's not surprise to me that phones have grown to have desktop class RAM specs. Many people don't know about it, but you van hook up a Samsung phone to a monitor and have a fully featured desktop right there waiting for you in DeX, you just need a Bluetooth keyboard+mouse to control it. I bet my parents could use a phone as a desktop without ever running into any trouble, partially because of how much RAM those phones sport.

If all you need is basic browsing and social media, you can go with 6GB of RAM, or even less. As time goes on, your phone will start to struggle with the ever growing websites and apps, but it'll keep doing what it always did, you just see a few more loading screens when switching between apps. Any €350 phone will do fine for most people these days, I don't get why people spend three or four times that on a phone if all they do on it is browse social media.