Country standards from the typewriter era. In Bulgaria we have a different layout from the Russian one, using the same Cyrillic letters (stuff like э and ы that we don’t use) but most people use the “phonetic” keyboard which is the one you describe. Also in casual conversations a lot of people don’t even bother to use Cyrillic and go with latin instead even if it’s not official or standardised in any way.
You get used to it. You just write the sound, sh, j, ya(often weitten as q), ch, yu. ь we barely use unless when you write what you would spell as ë in Russian, we don’t use that letter at all! We use a lot of ъ (sounds like uuhh). It’s usually spelled as y or a.
It’s usually more annoying to switch keyboards all the time, but typing in Latin script feels wrong and I feel like it changes my “written voice”.