I find it rather interesting, that 6-max has largely taken over online cash game poker, but online tournament players still seem to hang on to the more traditional 9-max or sometimes 8-max, which is just a small variation from 9-max. Sure
poker sites offer 6-max tournaments, but these are not the most popular or plentiful.
Personally I actually think, the 6-max format has some great advantages for tournament play. A 6-max table play more
hands per hour, and since you can get involved more, you get far more chances to actually play, before the blinds go up. In a 9-max tournament, sometimes you have been involved in like 3-4 hands, when you are already sitting on a push or fold stack.
For the same reason stacks tend to remain deeper in a 6-max tournament, which also leave more room to play and use skill edges. It is essentially the same as a slower structure without increasing the amount of time, which the tournament takes, and I personally find that brilliant. I do wish though, that the final table would start, when there are 9 players left. At that point it becomes awkward in my opinion, that the remaining players are still distributed on two tables.