I don't do FIBA, but having watched a lot of the FIBA stuff on TV, I can almost say the good reason for this is when reporting, you usually have to indicate 1, 2, or 3 FT's, so doing a jersey number 1-3 and then the number of FT's can get confusing to the scorekeeper. Remember, not all of those folks who work the book are 100% knowledgeable about how we report those fouls.