It’s one of the reason Apple decide to combine RAM onto their CPU/GPU altogether, seeing not as a independent part but rather together with CPU (and GPU).
And it’s not a terrible thought.
When you purchase a top-of-the-line processor, especially from Intel since they last longer, you can be using the chip for 3, 5, 7 or more years, during which memory requirement for tasks keep increasing. As such, instead of purchasing a brand new board (or device altogether), you buy some RAM for the upgrade.
It’s like the argument “yeah, stuff in cars break. So why bother replacing, say, the spark plugs when you can just replace the engine since the bore and piston rings wear out and why just not get a new car altogether”
But the cost of replacing a engine or a car is much greater than replacing spark plugs or reconfigure the ecu.
It’s also worth noting that modern devices are surprisingly capable – for example, I had played World of Tanks on a Intel Pentium 6405U. The only reason the platform will work is because I upgraded the RAM from 4GB to 16GB – something you can’t do when the RAM is soldered.
It’s about “future-proofing” the device – when I purchased the Dell XPS 9360, I thought 8GB of RAM is enough. One and a half year later, that was completely not the case. And the sad fact, is that the chip is immensely capable – it’s a i7-8550U. But I can’t use it to the full potential. This Pentium, however, I can. Because I give it the RAM to multitask.
Heck, I can probably crank to half res assets for KSP and keep it going, unlike on 9360 where I have to keep it quarter or eighth.
On the other hand, desktop motherboards and CPU sockets are less the case – since by the time you need to upgrade, new CPUs with new features (which require new motherboards) have likely arrived, thus there is not a lot of reason to keep those two independent. Unless you can swap out the different generations of CPUs, which is a plus in any way.
However, there are cases where physical failure to motherboards can happen, and this is when a detachable CPU can come in handy. Compared to DIMMs, however, it is quite less important.