Something that I think the physical sciences benefit from is the ability to look at a problem from more than one angle. For instance, the stuff that we think is the most important, such as the most general laws, is supported by many different kinds of measurements, plus the parallel investigations of theoreticians. A few scattered experiments could bite the dust, like unplugging one node in a mesh network, and it could either be ignored or repaired.

The social sciences face the problem of not having so many different possible angles, such as quantitative theories or even a clear idea of what is being tested. Much of the research is engaged in the collection of isolated factoids. Hopefully something like a quantitative theory will emerge, that allows these results to be connected together like a mesh network, but no new science gets there right away.

The other thing is, to be fair, social sciences have to deal with noisy data, and with ethics. There were things I could do to atoms in my experiments, such as deprive them of air and smash them to bits, that would not pass ethical review if performed on humans. ;-)