Meet Rachel. She is 15-year-old girl who wears heavy black eye makeup, slogan-spangled t-shirts, and skinny jeans. She has a 13-year-old punk boyfriend whom she snuggles mutely on the couch at family gatherings. She hardly ever addresses adults, although she is not unpleasant.
There is no singing or music at any family gathering if it happens on a Saturday, because the strictures of Rachel's sect forbid music on the Sabbath.
Or consider Krista. She is the youngest person in the office, and the older ladies are all keenly interested in her romantic exploits. However, they cannot talk about this when a certain other coworker is around - that coworker and Krista belong to the same church, which does not allow dating outsiders. Krista wants to keep belonging to the sect, and to keep dating outsiders.
We're all worried our teenage children are going to opt out of decorum, study, and community involvement in favor of being cool, with all of the hazards that entails. Religion used to be a safeguard against the tragedy of eternal adolescence. It wasn't just the rules that were important but also religious passion and spirit, and the tendency to get communities "all on the same page", behavior-wise.
When I first heard Dr. Laura railing against interfaith marriages, I didn't really get it. I didn't (and still don't) belong to a church so I couldn't really tell why it was a big deal. Now it seems obvious that mixing up different moral codes into the nuclear-family melting pot yields, not a random mix of religious codes so much as the most permissive mix possible. Similarly, mixed neighborhoods, schools, and institutions all put pressures on the individual to fit in, morally and otherwise.
The rituals to be observed are the ones that are the most fun. The rules to be obeyed are the ones that are the least inconvenient. It's not too bad to avoid eating poultry on Tuesday, but if I can't date all the Cathars, Copts, Sikhs, Scientologists, and Jeffersonian deists that I want, I'm leaving the church! It's been long noted that it is hard for church leaders to shepherd their flocks with so many distractions. It's only getting harder.
Yet few people are willing to resettle and form single-sect communities, and Communities are more complex than they've ever been - can a small sect guarantee that its town will include the requisite number of policemen, bookkeepers, dishwasher repairmen, and dogcatchers? What if the sect attracts mainly artists and philosophers? Are they going to contract out to non-members for vital services? If so, they are not a town at all, but a mere bedroom community. There's nothing wrong with that, per se, but your kids will still grow up hearing songs about suicide, group sex, and mass murder.
Moreoever, with no constitutional guarantee for freedom of association, single-sect businesses are probably illegal, and run into the same problems with today's complex workforce that the single-sect towns would. The problem of desiccating morals and civic life may not be solvable through religion - not in as thoroughly splintered an environment as the United States.