"may not lead users to a payment method other than Google Play's billing system. This prohibition includes, but is not limited to, leading users to other payment methods via: .... [lots edited out] links, messaging, advertisements or other calls to action".

The TOS specifically notes that things like tax deductible donations, payments for gambling, and physical services such as cruises and airfare ARE permitted to link outside of google play because google does not want to deal with those through Play in most cases. I think you are actually banned from using Google for those. So the key is a tax deductible donation - and a payment, even voluntary, to an individual in the US at least is not a tax deductible donation in almost all cases.

My sense is google is merchant of record, and can't control the delivery of those other types of services (cruises, airfare, wire transfers, gambling etc) and the related liabilities the way it can with digital stuff and apps - so Lyft would be allowed to bill directly and if a lyft driver assaults you and sues, google was not seller or payment handler.