I really don't see the problem with someone paying a deposit if that's what they wish to do.
However, that being said, I don't like getting deposits either unless rare exceptions of cross-country travel booking well in advance and if I see any red flags. Zelle s just fine and it's very instant just as Venmo is. I even have clients that Zelle the night before an appointment because they feel comfortable but course, as you said, there are clients that are regular. The biggest thing about clients and providers, if you will it's all about communication. The provider needs to communicate effectively on time and be professional about it, if they're not, then that would be a red flag for a client. If the client is not communicating effectively, then that's a red flag for the provider. I look at it as if you're setting an appointment for a doctor or an appointment to get your car repaired or reservation at a restaurant.
And I do agree there are some clients that try to scam the provider, such as, why don't you get a hotel room and then I'll meet you there and I'll pay you back. Well I did not just fall off the truck yesterday... So , both the client and the provider just have to be smart about it that's all.