Oh, I didn't mean most, just that there must be some. I've had transactions not get in the next block. And when that happens it usually takes a few blocks to get. Now that I'm thinking about it, maybe I'm wrong. The delayed transactions may only have happened when I sent ~10 and usually all but one would get in which means there aren't miners who only take fees. Maybe miners that usually take zero fee, but delay with some probability? Seems unlikely. I also thought I'd seen others having the same issue, but I didn't look carefully.
This was over a month ago, but I assumed it still happened and I just wasn't seeing it because I'm sending less often now.
At present, fees are nothing compared to the block reward. It makes no economic sense for a miner to avoid fee-free blocks.
Yeah, I wouldn't do it. But I could see people thinking "I'm going to be doing this for a long time and the sooner people get in the habit of paying fees the better for me". Like I said though I'm probably wrong. It was probably just low priority payments not fitting in that part because I was doing a bunch and they were small and probably new since I had been receiving lots of small amounts around that time.