Mining for pools where you are more than 1% can be rather difficult, and despite all the talk of decentralization it's actually provably less profitable to mine at a small pool than at a large pool. If it's not, then why doesn't everyone just stick with solo mining forever? Because you'll likely never find a single block that way, just like a small pool will only find blocks infrequently. A pool with 3% of the hash rate for example is likely to find about 2.7% of blocks in my experience, while a pool with 1% might only find 0.5% of the blocks. And a pool with 35% of the hash rate might find 37% of blocks. But that's a topic for discussion elsewhere.