As someone who plays youth hockey (18 year old), I can give you the source as to why kids aren't playing as much hockey: It's not on television. In HS, I played football and basketball and hockey in a seperate league.
I started playing all 3 early because all 3 were on television often and I got the chance to pickup all of them early, and I live in the SOUTH (Atlanta)
With Hockey rarely on television these days, and I mean all the time, it is easy to see why baseball, football and basketball are going to be more popular.
The show I watch nightly is Sportscenter. I never miss it. Along with SportsCenter I watch most of the sport specific shows like college gameday (football & basketball) nfl tonight, baseball tonight. The NHL should have signed with ESPN for lower to free to keep them on that network. NHL tonight was a great show, and I miss it. The coverage on sportscenter is abysmal and I wish it wasn't. The playoffs need to be on national television and some aren't. Point is, if it isn't on television I don't care about it.
Kids are lazier, but when they play sports, they play what they see most, and the dreams of playing in front of crowds and getting national attention is a factor. While most kids don't make the bigs, the thought of it is good enough to get someone at least started.
Also, hockey is a sport where a rink is needed. The other sports: football, baseball and basketball can be played anywhere, and equipment is much cheaper. Playing football in the street all you need is a ball. Baseball requires a ball and glove. Basketball needs a ball and a hoop. To play hockey, you need skates, a stick, puck, 2 nets, flat surface, it's a big hassle.
Overall though, building more rinks and making equipment cheaper combined with a greater television coverage package will once again keep kids interested.