It's not just the creators, it's also the backers. As soon as I am receiving something in return it's no longer purely a donation, but a purchase in some jurisdictions. This means, as a backer, I need to pay VAT (in Germany). There's a few options here: The service handles this for me, the creator does it or I do it.
If the creator does it they now need to deal with the authorities in multiple countries, that doesn't work for any but the really big ones. If I do it, I now need to collect the receipts and list then on my tax return to pay the VAT. Or the service just takes care of it for me, like Patreon does.
Honestly, if I had to deal with paying the VAT "manually" I don't think I would back anything.