OK, a few resources on raffles here.
First, there’s a help article on them: https://patreon.zendesk.com/hc/en-us/articles/204199489-Can-I-offer-a-raffle-as-part-of-a-reward-
In general, here’s the reason raffles aren’t allowed:
When a patron makes a pledge, they are guaranteed to get something out of it. When a creator offers a chance of winning something (whether that be as small as a sticker or as big as a car), then this steps into the territory of giveaways/raffles. In order to comply with state gambling laws, Patreon has to ensure that creators are not offering this type of content.