There are three clear benefits.

1. Answering where humans come from is probably one of the the oldest question we have had. All religions try to answer this in one way or the other. I say, trying to come up with scientific answers is extremely valuable.

2. We feel awe at the wonders of nature, not much different from the awe that we feel when we see great human art. Tax dollars as well as charity are used to subsidize art often. This is similar, though there is more money involved here.

3. The problems one sees in different domains are always different. Funding agencies give money to the "directly economically useless domains" because the workforce that is trained and technology that is developed can then be applied to the "directly economically useful domains". The support money to the former is much smaller than the support money to the latter, but just enough to inject fresh ideas and creativity to the latter.