Porkchop,
I'm carrying 220 on one league and right at 230 on another. I've got 4 300's in practice, but none in league. My sanctioned league honor scores are a 297, two 290's, and one 800 on the nose (264, 268, 268). I've had a couple of 770+ sets.
I think the reason that some people carry a high average without any 300's (like me and you and probably others too) is because when it comes to shooting a 300, you have to be perfect and strike every frame in a single game... but when it comes to shooting a big set like an 800 or 770+, you don't have to be perfect on every ball in every game - you can mess up 1, possibly 2 times (as long as the mess ups are spare-able), in each game and still shoot a big set, therefore helping you or me still carry a big average.
My 2 cents...