Science has seriously investigated plenty of ideas that have lacked explanation. For instance when Newton's law of Gravity came out, there was much arguing over whether to accept the action at a distance which was implied. Similarly Einstein's explanation of the photoelectric effect was seriously considered even though nobody had an explanation for how continuous waves could be acting like particles.

A much bigger issue is lack of evidence. For instance there is no personality test that has been shown to have a positive correlation with your Sun sign. Plenty of people have tried to find one, but with a uniform lack of success. This is pretty strong evidence against astrological theories about how personality is supposed to correlate (albeit with many complications) with your Sun sign.

Cheers,
Ben