Intriguing Theory About Spacegoing Aliens

Somebody pointed out something I should have thought of (It's now being touted as a stunning discovery, but it's only an interesting thought).

Based off of the evidence so far, it is possible that Earth is, as far as habitable planets go, a wee bit on the small side.

A smaller planet has lower gravity, a larger planet higher, as a general rule. There may be exceptions (and it may be sample bias, it's easier to find larger planets than smaller ones).

So, here's the thought:

The higher the gravity, the harder it is to get off the planet. Some of the "super earths" we have found may have an escape velocity literally too high for chemical rockets.

The larger the planet, the lower the pressure of population and the higher resources on the planet.

In other words:

If you have a larger planet, it is both harder to get into space and you are less motivated to do so.

Which could reduce the number of space-faring civilizations and thus our chances of contacting one.

(And could also, writers, be used as a handy dandy explanation if you want a lot of planet-bound civilizations).

So, why haven't we thought of this before? Somebody give me a story in which somebody actually remembered this rather basic fact of physics...that way I can feel like even more of an idiot.