Maybe the reason you keep asking "Why didn't anyone tell me this?" is because you are the one to teach others about it.
Went back and watched the Bieber set at Coachella given the “If so and so did this” discourse all over the feed.
1. He sang 13 songs that were not part of the YouTube set.
2. The YouTube portion was him also singing along to some of the stuff that made him very popular initially.
3. He performed another 5 songs afterwards.
Any outrage over that is manufactured — at best.