Shout out to forms which error out with "Password too long! Must be at most ten characters. All from this subset of ascii". Which seems especially popular with banks.
They buy someone out, and now there are two systems. Glued together with duct tape. Then they release a new web product, or mobile app, or whatever, and that gets taped on too. Duct tape and spit all the way down, with everything eventually limited by the most broken part (if you're lucky).
But modern apps: just give us Unicode support. And maybe a limit of 255 characters, but not less.