Less common and I might be mangling terminology , but there's also PCIe, PCIe-Mini, mSATA, SATA Express (same connector as SATA). There's also a variety of m.2 form factors

Don't forget U.2 - NVMe in a (usually) 2.5" form factor.

There's also M.2 "M key" and M.2 "B key" because why not have two different types of connector in your brand new standard. There's also "M+B" which reminds me of the days of CD-RW and CD+RW with CD+/-RW thrown in to try and unify things.

https://en.wikipedia.org/wiki/M.2

This is annoying because some dual M.2 adapter cards have one of each, so you can't use two M-type cards in it.

Because this fixes the issue of "i plugged it in but it doesnt work" issue, as you already know it wont work because it doesnt fit. Kinda like DDR slots

If DDR memory had screws I'm not sure we'd be happier. We'd be bitching all the time about the freaking tiny screws that kept getting lost in the case.

I can't think of another standard made so deliberately difficult to install. A distant second is the 6/8 conductor PCIe power connectors that are a giant pain to use. Why couldn't they just force 8 for everyone and be done with it? Instead we have these crappy split connectors.

I think it was made due to laptops. Everything has to be flat. Using clips like on DDR wouldnt really "fit" as then youd have a waste of space, and DDR is a generic component nowdays. The other option is to use PCI-E cards, of course.

Make a screw-sized clip. Done.

I’m rooting for SCSI to make a comeback - I have a box full of cables ready to go!