Agreed. PBS SpaceTime posted a really excellent episode the other day outlining the challenges that silicon-based life would face in (most) natural environments. I, like OP, had long assumed that our preference for "life as we know it" was a bit of a blind spot -- I no longer think so. There are so many obstacles standing in the way of the organic evolution of silicon-based life that it wouldn't make sense (in most environments) for nature to favor silicon over carbon.

Given a) the goldilocks scenario that gave rise to life on Earth and b) the apparent dearth of life elsewhere, I think it is reasonable to suspect that it is very difficult for complex life to spring up just about anywhere. Silicon-based life would face an even steeper degree of difficulty. Environments without water (an ideal solvent for the mixture of molecules) might just render the appearance of complex life next to impossible. We can't know that for certain, of course, but I think it's completely reasonable to narrow our search (for the time being) to environments that seem conducive to life rather than expending energy and resources on locales where we have no reason to think that life is even possible.