PS. I rarely see such in tablets. Why?
Mainly because the tablets are under a lot of pricing pressure. On your average PC with 100's of gigabytes there is space to install languages. In a tablet you don't get cheap space so to change languages you install (commonly called flashing) the replacement OS and to make matters worse or more fun (?) such a change is rarely supported by the maker.
This question seems to pop up when folk buy a tablet in some other country and then try to use it.