Statwhores suck. Any stat that's tracked will get whores trying to maximize theirs.
So... under the current system, we get people whoring for time, to get their stars. Then they find that people won't play them, even though they're really nubs who've played a lot of SP with bots, but they made an "online game" so the time counted, and they smurf so that they can play with nubs like themselves
So... let's put it another way. If all stat-tracking systems inherently suck, but can do useful things for players in terms of some idea of who they're dealing with... isn't the minimal good well worth it, vs. the absence of any good in a system that measures nothing about a person's play at all?