We learned his schedule, we made sure to make his drink so it would be ready on time while also handling the hundreds of other orders in the morning rush. This is something we tried to do for every regular customer with a fixed order.
I'd argue that this sort of thing is well within the bounds of what was 'tippable' service back then.
But to be clear, tips weren't expected then like they are now. It was an infrequent thing. If you dropped your ~15¢ change into the jar once or twice a month, you were a generous tipper.
We served Steve for many years and he was definitely an outlier. He wasn't the only other customer that never tipped. But he was the only one that was famously rich, which is what made it so amusing to us.