I guess it could work well for sets of strings that you know will not go above a certain length? But after that it might become painful, i.e. the algorithm complexity will start depending on the maximum string length
When sorting single words consisting only of the letters A-Z, for example, you can think of it as the same thing but with 26 buckets (27 if you pad with spaces instead of As) instead of 10. Or you can think of it as a specific subset of numbers in base 36, if that makes more sense to you.