Personally, I think every active h2h league will have streaming. It's a strategy. I've ran Yahoo leagues for almost a decade now, and basically what I do is set a 110IP soft-cap. If a team uses a spot-start for any reason (picking up a pitcher who starts within the next 2 days and dropped within a couple days of the start), then the 110IP becomes a hard-cap. Team's cannot go over that limit or they'd be penalized.
Team's are allowed a max of 3 spot starts per week. I also have an 8 day rule, which in short, prevents teams from picking up a guy and dropping him after his 2nd start in the week (it counts as 2 spot starts).
Basically this allows teams to moderately stream if they need to, and allows other teams to accumulate as many innings as they want if they have a huge pitching roster without penalty. It's something that has worked very well for many years.