Why do firms get merged or acquired?

This question is asked at the Economic Logic blog. There are a number of possible reasons, one of which could be to get the firm's workforce.

Paige Ouimet and Rebecca Zarutskie show that mergers and acquisitions can also be the result of a drive to get access to the other firm's pool of workers. This is particularly true when the labor market is tight and the workers carry high human capital.

I can't help but think there has to be more to it than just a workforce. After all if you just want the workers why not employ them directly? Why buy a whole lot of non-human capital if you don't have to?

The likely answer seems to me to be that you do want the non-human capital. The likely reason you want the human capital is that it highly complimentary to the non-human capital. And buying the firm gets you both.