> Custom built PCs are a niche. The vast majority of people just want to buy a box that works.
That is why I wrote
"(or often rather: let a good friend build one)." :-)
Seriously: In my opinion (but others might disagree) an advantage of self-built PCs over one that some company produces is that you know exactly what components are inside (in particular you can buy components in which you trust), which makes you far less dependent on driver support by the manufacturer (i.e. you can find drivers in the internet by yourself if necessary). I often had bad experience with driver support by manufacturers (expect for a few well-respected names).
Also lots of cheap PC manufacturers install lots of crapware by default, while your self-built one is a very clean install.
In summary a self-built PC often "just works" far better than a pre-built one.
You're forgetting the most important reason to DIY: money. Where manufacturers are happy to charge you 2x the price to double your RAM or put in a non-shitty SSD, DIYing can shave off a few hundred Euro.
Just as an example, over at apple.com, the new iMac comes with 32GB of DDR4 2666MHz ECC RAM. To add 32GB (64GB total) they are charging 960€, or 2,880€ to add 96GB (128GB total).
Looking on amazon or geizhals.eu (price comparison site), 16GB ECC DDR4 2666MHz sticks cost 200-220€ x 2 = ~450€ für 32GB. That means you can save 500€ on just RAM alone.
Same applies to SSD storage. And graphics cards. And CPU. And basically anything you could want to upgrade.
> Just as an example, over at apple.com, the new iMac comes with 32GB of DDR4 2666MHz ECC RAM. To add 32GB (64GB total) they are charging 960€, or 2,880€ to add 96GB (128GB total).
Specifically Apple is well-known for their expensive pricing for better optional components (which is often necessary to pay, since for many models you cannot simply replace the component (RAM, SSD etc.) by another one on your own).
That is why I wrote
"(or often rather: let a good friend build one)." :-)
Seriously: In my opinion (but others might disagree) an advantage of self-built PCs over one that some company produces is that you know exactly what components are inside (in particular you can buy components in which you trust), which makes you far less dependent on driver support by the manufacturer (i.e. you can find drivers in the internet by yourself if necessary). I often had bad experience with driver support by manufacturers (expect for a few well-respected names).
Also lots of cheap PC manufacturers install lots of crapware by default, while your self-built one is a very clean install.
In summary a self-built PC often "just works" far better than a pre-built one.