I don’t have the tools or skills to replace soldered on memory chips when they fail. Nobody at my place of work does. Nobody was doing that type of work in a warranty centre I worked in either.
I’d need to buy an entire motherboard which will much more expensive, and likely more time consuming, than swapping a couple of memory modules.
One time upgrading workstations, 4 of the 20 Corsair kits were sent for RMA. Those aren’t great odds.
I would guess that soldering them to the board reduces the points of failure, the slots can and do fail. However, I’ve also seen soldered components coming off as the cause of failures, but it is usually a part that gets hot combined with a design flaw.
That being said, I really did have one bad stick of RAM once in my life, and it really does cause strange seemingly random problems.
Plus, no way to put more RAM/replace RAM with larger module if it's soldered on.
I think making it impossible to upgrade is a somewhat bigger problem, at least while the machine is still in-warranty.
Traditionally, RAM has been one of the more-common upgrades to make as needs or budgets change, so soldering it in looks like planned-obsolescence.
99% of people will not be replacing the USB-C port, they'll just bin the device and buy a new one or live with a dead port. So the effort is 80% PR 20% actual usefulness.
I am waiting to jump ship to a different manufacturer, but nobody is challenging ThinkPad on keyboard quality/layout and Linux support, the two factors where I'm totally unwilling to compromise. (Tuxedo is close but still not the better alternative.)