0 is only "usual" because that's what C did, and a lot of later languages slavishly copied C syntax. By default in Fortran arrays are 1-based.
In Ada there is no default and you have to pick the beginnning and end ranges. Interestingly, it seems that most code I've come across picks '1' for the lower bound. I think that's a pretty good indication of where folks would have gone given a free choice.
