Also they don’t have a player that can move between live and VOD like YouTube’s. If it were easier to jump back to before the ad and play at 1.25 until you catch up it’d probably be less annoying to the users.
This is a big reason that I will watch a stream on Youtube if a streamer simulcasts on both. The Youtube player is just such a better experience than Twitch's and I already pay for Youtube premium so I can also avoid ads.