I think there are a lot of factors that have contributed to the decline. There are so many thinks for the kids today to do hands on. Watching is boring compared to doing. Even if its just texting. Another reason is the sheer number of channels on TV to chose from. I have like 250 on mine right now. When I was growing up I only had 3 and so when baseball came on it was great. Even if it was in black and white. At least I missed the radio era.
I think the game is going through a bad time also with all the PED problems. That turns kids off also.