Not surprising. YC founders are blessed creatures who are (or will be) indoctrinated into the Thiel Zero to One philosophy of building a monopoly. If the monopoly doesn't exist, why should they care ;)
OK all jokes aside, honestly two things at play:
(1) Impossible to keep tabs on the whole space all the time. No matter how hard you search, you always miss things.
(2) Some amount of (proper) competitive research is really good (for obvious reasons), but at the end of the day--you gotta get on with doing your user research/building/testing testing.