Why doesn't Twitch take 1% of donations to streamers?

It seems like they're leaving a lot of money on the table. I don't think a significant number of people would jump ship if Twitch updated their policy to give 99% of donations directly to streamers while taking a 1% cut for themselves.

There might be some initial grumbling, but it would probably fizzle out in a week when people move on to other things.