TikTok gifts are not charitable donations. They are in-app purchases. For every gift you buy, streamers earn "diamonds" which can be withdrawn for cash.
You cannot built this kind of functionality without giving Google/Apple a 30% cut, plus they collect sales tax and VAT on your behalf.
I'll give you an example. If I sell an in-app purchase for a price of £1 in the UK, £0.17 go to the government, and £0.25 to Apple/Google. I'm left with £0.58!