The Lakers tend to be reluctant to make big mid-season moves because of the learning curve of the Triangle offense. However, they know they need better point guard play, and have some assets (over $15 million in expiring contracts, Jordan Farmar) to make it happen. Kirk Hinrich seems like an ideal fit for the them, though his contract isn't cheap. Otherwise, it's tough to find a point guard that makes sense, due to the unique nature of the Triangle.
There's also this: they might be good enough to win anyway, so why risk it? They're already paying a huge luxury tax bill, so why pay more to make a marginal improvement? They won it last year with this mix, after all.