The Mavericks have shown that it's not really worth it for them to make the playoffs---or, depending on how you phrase it, that they don't deserve to. While recent games against the Spurs and Thunder, 2 of the 3 best teams in the league, were close, hard-fought, and not at all what you'd expect from a 10th place team against those behemoths. It was nevertheless obvious where the balance of power in those games lay and while it's still just possible the Mavs will make the playoffs, it's not real possible that they'll make the playoffs and NOT have to play the Thunder or Spurs.
That being said, the dirty little secret about the Mavs right now is that they're...kind of good. In fact, if they keep clicking along this way, they might be really pretty darn good. They're not winning 12 in a row, like the Nuggets, or 23 like the Heat, but outside of a blowout loss to Houston the Mavs they haven't lost to anyone but the West's absolute elite (Memphis, San Antonio, Okc) since the end of February. And there's only two more of those games on the schedule (Clippers, March 26th, Memphis, April 15th). That's not to say that the Mavericks are going to win every other game.
It's to say that they could win every other game. At least, while it's unreasonable to think they'll win "all", it's reasonable to think they'll win "any", or "any given night". And even if you take the ones they're likely to lose--Denver and the Lakers, for example--it's not unreasonable to think the Mavericks could end the season on a 10-5 tear, finishing at 42-40.
Why would they do that? Well, for many that's a self-evident question. Feels good to win games, feels good to have some hope for the future, to keep Dirk happy. But even for you tankers, all of the teams the Mavericks trail in the standings already are over .500, so it hardly seems like getting a couple of games above it is going to do much damage--and other than Portland, the Mavs would have to go five games under whatever Philly and Toronto do for the rest of the season to sink any lower. And THAT is a tall task.
So there aren't many stakes to winning. Even if they make the playoffs, they'll be playing teams they almost certainly can't beat. But, they'll keep at least one streak alive and they'll win some games and if you mind either of those things than you, my friend, might be a Grinch.