The money they earn from donations is used to keep the stream going. Not buy them a big house, not so they can live a nice life. It's just to keep the stream going. Most of them are sponsored, they get played similar to how people get paid on YouTube (and most of the have YouTube channels as well), they also run ads whitch sometimes gives them money. And sometimes give Twitch some money. The ads, the sponsorship, and YouTube is what gives them money. And most of them are married. Trying to do whatever the can to support their family's. Must Be Working Out For Them.