Probably the same reason that PROTESTANT attendance is also down. (And Protestant churches never had Sunday worship as an obligation.)
Those reasons include a lot of factors. First, Sunday is no longer a ‘day of rest’ as it was even 50 years ago (some of us remember Blue Laws. Hard as it is for the mall rat of today to believe, stores were not open on Sunday!)
There are many more activities available on Sunday. Years ago it was UNHEARD of to have sports practice or games (in the schools) on Sunday. Now it’s routine. If you have kids getting up at 4 a.m. for hockey practice Sunday morning, hubby heading off to the links at 9 a.m., and teenage Muffy with a mall date for noon, when do we find ‘room’ to fit church in?
Poor catechesis indeed has led to people feeling that since God is ‘everywhere’ they don’t NEED church.
Or they’re too ‘tired’ to get up at 8 a.m. but think nothing of heading out the door at 9:30 to go shopping or out to brunch.
And there’s a lot of ‘picky eaters’ so to speak. “I’d go to church but I don’t like Father X who is too strict, too lazy, too pushy, too laid back, too loud, too soft, too new age, too mediaeval.”
The Church is “too big, too small, too ornate, too plain, too much singing, not enough singing, too hot, too cold, too impersonal, too nosy.”
The people there are “too ethnic, too similar, too ‘strange’, too ‘dull’, too quiet, too shrill”. . .
The Mass times are too early or too late. . .
You get the drift.
