Twitch is continuing to roll out the many upgrades it promised at TwitchCon. As of today, you can gift 1-month subscriptions to anyone on Twitch, regardless of the tier. They don't auto-renew (you "currently" have to buy every month), but this could be helpful if you have a friend who can't afford to subscribe but wants to enjoy some of a channel's perks -- say, a subscriber-only Discord chat. It's useful for streamers, too: they can hand out subs as prizes for contests.
To help make use of gifting, Twitch is partnering with GameWisp on an extension that lets Affiliate and Partner streamers highlight viewers they believe deserve a sub gift, like an extraordinarily kind chatter.
As with Twitch's other recent additions, this is as much about helping its own service as it is streamers and viewers. The easier it is for people to subscribe, the more incentives paid streamers have to keep broadcasting and interacting with their audiences. And of course, at least some of those who receive gifts will like the experience enough to pay for subscriptions on their own.