I have read that, if you tip with a card, the business gets it, and they may give it to the staff, and they may not. But if you tip by leaving cash on the table, the staff for sure gets it, and the business can't stiff them. So, yeah, the staff probably prefers it.

Tipping is about the only time I need cash. Outside of restaurants, most people I need to tip do not have an easy way to receive digital payments.