All typing machines used it, but it was awful for programming obviously, so the "Polish programmer's layout" was added, and because it was exactly the same as standard american QWERTY (except for Left Alt + some letters) it won almost overnight.
Windows still shipped with both layouts enabled for Polish locale for decades, and nobody used the typis one, but there was a shortcut that changed between them.
When you accidentally used that shortcut - if you had Y or Z or Polish letters in your password - you couldn't log in (because you typed "yeti" but got "zeti" but it still looked like * * * * :) )
I think there must have been millions of USD lost on support calls because of that little shortcut :)
If I remember correctly shortcuts to change layout/language are by default Ctrl+Shift and Alt+Shift respectively (correct me if I'm wrong). These are incredibly annoying, especially in some games. Luckily though you can disable them from the settings. Instead there's Win+Space, which is a Godsend and should've always been the only default.
Fun fact: on Windows Polish programmer's keyboard you can use the Tilde key (Shift+Grave) to input Polish characters as well, e.g. press Shift+Grave (it won't put in any symbol at this point), release and then press 's' to input 'ś'. However it makes it problematic to input the tilde symbol itself, so I've modified my layout with the MS Keyboard Layout Creator to get rid of that functionality/flaw (aside from other minor improvements) https://www.microsoft.com/download/details.aspx?id=22339
The shortcut to change was definitely something with Ctrl and Shift because I remember accidently switching layout when I was selecting text by whole words with Ctrl+Shift+Left/Right.
Tilde works funny on linux - it makes alternative version of every letter, not only from the current locale. I was accused of being a Russian pretending to be Polish on some Polish forum long ago because I wrote something with a Greek (or cyrylic?) letter by accident because I did something with home directory in the background and only pressed ~ once instead of twice :)
Some people move to BÉPO or something like that, I use QWERTY with Xcompose.
We've retained x y q (no purpose in our alphabet), making it quite convenient to just type using the native keyboard layout, regardless if I'm writing in my native language or in English.
à â ç é è ê î ï ô ö ù
on the right of the keyboard: ù
but that's enough to want accents and symbols on the number row by default (&é"'(-è_çà) and numbers when pressing shift.
I think that's the reason that bépo (a French variant of dvorak which allows easy access of both common accentuated keys and numbers) is more popular among French speakers than dvorak is for English speakers, proportionally.
I have never seen anyone use an Alt+number to get these, I personally default to EN layout and switch only when I write in local language.
In Polish we have 9 such characters and most people use just so called "programmers keyboard layout" which uses left-alt + letter to do the accent.
E.g. alt + e = ę, alt + l = ł (with a one case where we have two different accents for a single letter: z, so we use alt+z = ż and alt+x = ź, the second letter is less commonly used then the first one)
20-30 years ago there were some strange keyboard layouts that didn't use alt, but hopefully they were forgotten.