Is it really worth getting up early for a worm? Sure, the early bird gets a worm, but nowhere does it say that the later bird can't also get a worm…and he got to sleep in! Plus, there are lots of worms crawling around at night, which means maybe the LATER bird gets the most worms.
The point of this expression is that there is great benefit to getting an early start, but we are only looking at this from the bird’s perspective. What about the worm? Presumably the early bird ate an early worm who felt like getting an early start and his ass got eaten! If that worm was lazier, he might still be alive.