I think this is the case for a lot of people in their 30s; the desire is still very much there but there are too many conflicting commitments (partners, children, 'proper' jobs requiring long hours, commuting, housekeeping and so forth).
Up until even 6 months ago I used to still sink quite a lot of time into gaming (main thing I did/do when home alone) but then my son was born and you just don't get enough time for anything more than the occasional hour here and there in the late evening. 'Serious' gaming i.e. clan play, voice comms etc is definitely out of the window.
Anyway to answer the OP I actually don't think it is really a case of previous generations 'growing out of' gaming, more that they never grew into it in the first place. The majority of people over the age of say 40 probably never really had much of the way of gaming available in their younger (pre-teen) years.