Hmm. Selection bias perhaps? How many medical devices, nano materials, chemical sensors and life science, etc. startups applied to the last Y-Combinator cohort? The hundreds of hard science teams I see every year don't send you applications.
Maybe some of them should. Sure, the direct experience of most of the YC partners is web-centric, but they're connected enough in SV that YC might be a big benefit, especially if any of those teams are amenable to a 3-month build cycle.