Drive letters feel obvious from a user perspective, and I presume that's part of the reason for their invention - each physical disk (or partition) gets a letter, and we're done! Problem solved.

The Linux paradigm is pretty different in that every device is a file, and files can mount anywhere. (And that really does mean every device, not just disks. Even your mouse is a file and you can read mouse events via the filesystem)

The approach has a huge amount of flexibility. Most obviously, file systems can logically mount anywhere in the directory tree, so you can organise disks and network mounts anywhere you want them and never run out of letters.

It's a perfectly reasonable pattern for example to want your OS files to be on one partition, and your user home folder where you store your files on another. On Windows that would mean ignoring all the default Documents, Pictures etc folders, trying not to use them (and making sure other apps and programs which like to don't) and using D:/ for files. On Linux you can mount your storage right in your home folder, and everything still works just as it would if it were a single disk.

I can see why you miss Windows, but the unix-like approach is a powerful abstraction when you're used to it - just quite different.