You certain thats not bi-directional, or more likely - the other way around? As a single person who can go do fun things at the drop of the hat without having to get permission from someone else, or set up a babysitter, or any other number of roadblocks, trying to set up an outing with married with kids crowd is incredibly irritating, time consuming and often fruitless.

A lot of this is simple scheduling pattern differences.

As an example, my no-kids friends typically schedule things like dinner parties starting at 8:30pm or so. The ones with kids would aim for 5:30 or 6 instead.