I've come to the [somewhat] depressing and frustrating conclusion that the pax is either a tipper or a non-tipper, and it doesn't really matter what we do as their drivers. The non-tippers will always be the cheap-ass, obnoxious frugal Fannies, regardless of how helpful, fun, or kind you are to them. The tippers, otoh, go into the trip with full intentions of tipping no matter what. If the trip's atrocious, maybe they'll hold off. But otherwise, their driver gets a tip because the tipper was taught proper tipping etiquette while growing up, and they actually have manners and are decent human beings.
The part that sucks donkey balls for drivers is that the ratio of tippers to non-tippers appears to be 1:10 on average.
I blame the shitty richardhead parents of the folks with no manners or etiquette. But it's OK, the non-tippers will eventually fail at life in general because they lack social cues and basic skills that are necessary to thrive during ones lifetime. Most of my non-tippers are young adults and they haven't realized yet that their futures are doomed.