They certainly could, but what happens if they lose all their Patreon subscribers, Patreon goes down, they are banned from the platform or lose access to the platform, or their account hijacked?

For the purposes of discussion, assume that the Patreon user is operating in good faith and complying with applicable laws and Patreon terms of service, but were banned because of an insider threat, for example.

Patreon is fine and good, but is also a single point of failure. If you lose access to the platform, there is no portability or escape hatch. You're fully locked in, or in the worst case scenarios I outlined above, locked out.