I think it comes down to the fact that most people who make $300-400K have two parents working. (ourselves included).
Having two parents navigating the 9-5 slog around DC plus taking care of young children (or school aged kids which personally I have found harder with two working parents) is a never-ending grind.
There's a feeling of, "there has to be more to life than this".
I love my job (this is not a SAH vs. WOTH debate) but it's pretty crazy to plan the logistics of having both spouses working. I feel like all we do is work, commute (and we live close enough that one spouse bikes), and take care
of the kids. Lather, rinse and repeat daily.
Sometime I wish we at least had fabulous vacations or gorgeous furniture for all of our effort.