Is it because Microsoft stopped advertising that they exist?

yea. pretty much. they certainly don't make it known that it does exist.

1 time fee over monthly anyday.

as far as pricing. if you're gonna pay for cloud storage somewhere, anyway..

i know it kinda sucks ass, but you're basically paying for that extra onedrive space and getting office 'free' while you do.

so it does make sense for some users.

but for the love of clippy, don't share a cheaper 1 user/5pc 'personal' plan with other people because they also share your onedrive space. that can get messy and/or really awkward, really fast. get the one you can share with other users and add their msa to your 365 sub.