Thousands of patreon, GoFundMe, Kickstarter, and onlyfans disagree.
The problem is not the tipping. The problem is they can't do it because they are worried about being an MSB.
Discussion
Most of those aren't primarily tipping sites though. The major use case is often purchasing a product vs tipping.
Patreon is billed as a way to tip but in practice is often used for additional benefits for members.
Most people donate to the Kickstarter for the perk they get vs tipping a creator for an idea.
OnlyFans is to gain access to additonal access to creators.
The only one that doesn't have a direct product you get is probably GoFundMe but I think the charitable feeling is the product you're buying there.