Probably the same reason that the toothless and clueless SEC missed Madoff's scam right under their noses.

Even though the "bonuses" are a small fraction of the bailout, it's the principal of the thing. There is a so-called "clawback" option which almost always has failed in the past, but may work here.

Congress, especially the House, will be extremely resistant to any further bailouts, so the banks, auto industry, etc. had better have their act together to wisely spend/invest what they have been lent so far.