30-30 had a big head start on the 30-06. 30-06 won't overtake due to the many, many cartridges that compete with it nowadays. If they were the only two, then 30-06 would dwarf the 30-30, eventually.
Anecdotally, the 30-06 was considered a newcomer and often too much gun when and where I grew up in the '70s.
