This does not change the fact that removable storage (or even storage that's accessible post board-failure) provides an additional margin of risk mitigation against hardware failure. AND a convenient way of making bootable backups you can swap in the event of storage failure rather than taking the entire machine out. AND upgradability.
What's the advantage of soldering the SSD to the board?
(And personally, I've experienced boot failure hardware issues on two laptops, theft zero times.)