Why don't we see Others? I think the anthropic principle neatly explains both scenarios: why we're here, yet nobody else seems to be.
If life nucleation density is arbitrarily low (e.g. 1/visible univers) we still wouldn't fail to observe our existance. It is also worthwhile to mention that the deep universe is young, and hasn't yet bred sufficient amount of metals (in the astronomic, not the chemical sense), so due to delayed hatching we're not yet in the lightcone of an advanced culture. I.e., don't look at the visible universe without a probability bias, proportional but thresholded (no H/He life for sure). It is relatively straightforward to show that an advanced culture is expansive, in fact relativistically so, and everything past pioneer wave will be transformed to become unsuitable for an ursoup. Arguably, we're about to enter that expansive stage (notice that computational physics seem to allow cognition at a >>10^6 speedup, so the time from zero to hero is less than a year), and we've only become observable within less than a century, the high-power emitters less than three decades. What's the probability to observe a >>0.9 c pioneer expansion wavefront, which will kill subexpansive observers (observation window: about a century?), will prevent emergence of new observers, and will only start in systems with sufficient metallicity, with a yet unknown (yet probably very low) nucleation density? Arbitrarily close to zero, obviously. So I would be very, very surprised if SETI people actually found the sky hanging full of ~lighthour 300 K blackbodies, or even if we found independant life nucleation events within our solar system (which have to compete with impact ejecta crosscontamination, a very frequent event).
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