I think various french speaking regions outside France do use single words for those. E.g. in neighboring Switzerland I learned 70, 80, and 90 as septante, huitante and nonante if I remember correctly (I'm from the german speaking part)

Yes, they do. Belgian French has "nonante", for instance, which would be better, but which just never caught on in "standard" French. It appears in my Cassell's French Dictionary, but it's marked "dial." for dialect.

But they actually did! Septante, huitant/octante and nonante are real French words. Only the French don't want to use them.

Note that you cannot use heptante for septante.

It's also weird for 50-59. English does not say "fourty twelve" ("quarante-douze").

Neither does French, you're confusing 50 with 70. https://frm.wiktionary.org/wiki/quarante-douze

Edit: 50, not 60.

At least in Belgium we fixed that with "septante"

But making things completely logical would have been too much for us so we kept quatre-vingt.

It's weird form 70-79 as well! To say 79, you need to say sixty-ten-nine!