As I've got older, I've learned to appreciate how many of the greats just sit in that pocket and often refrain from being too flashy, unless it's that right 'moment' for a huge fill or whatever. When I check out YouTube videos every now and again of people showing off their drumming, there are so many that tend to just go for fill after fill, and you lose that sense of rhythm. Grohl kept it very simple at times, and it worked for the music that Nirvana and early Foos were trying to do. Something like Heart Shaped Box is really, really simple, but it sounds great for it. In Bloom off Nevermind is another that sits well. It fits in with what the bass, guitar, and vocals are all doing. Grohl having that knowledge of being able to play those other instruments probably helped him with keeping those drums tight, so they never once felt out of place or took away from the rest of their songs. It's good musicianship. On a semi-related note, I often think of his fills as being written sorta like guitar riffs. You instinctively know which fill belongs to In Bloom, or which one belongs to Heart Shaped Box, or whatever. I feel the same sorta way about Chamberlain's fills.