But you did suggest they're doing this "so you don't have to", which has the connotation that they're doing us a favor. I'm pointing out they are only doing themselves a favor.
The whole point of a free market sale is that you're both doing each other a favor. You'd rather have a trip home than the money in your pocket, and I'd rather have the money in your pocket than the time/expense it takes me to give you a lift. It is a service industry even if it isn't charity.
Since we can't exactly force rationality into individuals, nor can we force buyers to not give their money away, the pragmatic solution is to limit what is considered a rational maximum price on sellers. If you as a buyer still choose to pay more, that's all you, man. Society already warned you.
How can a buyer choose to pay more if the government regulates the maximum cost of a ride?
Hey, if word gets out that people are willing to tip extra, you'll get your results of getting more drivers out there and more people getting home. So please, if you really believe what you're saying, go out there and leave those big tips yourself.
Tips are just part of the price if they're negotiated in advance. If they aren't negotiated in advance then they have no impact on the availability of the service. Nobody is going to go out in a storm hoping that somebody is going to be nice and give them a big tip.
Tipping after a service is rendered really doesn't make that much sense economically unless you're a regular customer (in which case you're really just tipping way before the next service is rendered, which is why it works). Having payment based on performance certainly makes sense economically, but only if both parties are bound by the agreement.