It's a fad, pure and simple. Just like Truck Nutz and Calvin pissing on Chevys or Fords and and yellow ribbons and "Baby on Board" signs and suction-cup Garfields and personalized license plates and 76 balls (or Jack in the Box heads) on antennas and thousands of bumper stickers before them.

People like to decorate their cars. Other people spend time and energy trying to figure out how to cater to the first group. Here we have a guy who figured out something that people would buy, and they're buying 'em.

It's a way of customizing as well. Everybody thinks their family is special and wonderful and unique. Look, we've got three kids, a dog and a cat -- everybody's is different! (Sort of). People LOVE stuff they can personalize.

Gay families may be hesitant to advertise that fact on their vehicle, given the possibility of driving around in places where two men plus kids or two women plus kids (or without the kids for that matter) may incur a threat of violence. Just like a person may be ill-advised to drive around rural Alabama with a "I Support Gun Control". Unfortunate but true, and yet another example of hidden ways in which homophobia (and racism) lurk in places people don't often think of. The example I like to give is, what would be the reaction if this family tried to rent a motel room for the night in a conservative rural area, and how would that differ from my own straight white family?

It's a warning. As seen here:

http://www.sheldoncomics.com/archive/070923.html

http://youtu.be/xv-0Sr-BV5A

This video perfectly captures my biggest concern with these. Families are not static. What do you do as they change?

Every time I see those I always notice how the man is the first in line.

Maybe it's meant to remind drivers that the man is the head of the household and women best not be steppin' on his authority?

It is a small demonstration of being proud of your family and wanting others to know. Instead of posting an actual family photo (which is an action that has its own privacy and security concerns), it allows the person to say graphically, "Hey this is my family" or tribe or flock (if you will).

Flock? Yeah, not to be outdone some enterprising bird person has decided we shouldn't be left out of the fun.

Here are the feathered family equivalents. (You'll find one representing your little mischievous lovebird sprite, too.)

I've seen these with a Gay/Lesbian family & kids before, and I think it's delightfully subversive.

I would help you with your question, but I am still trying to figure out why put the "fish" on your car.

Will I be less likely to rear end you if your Christian???

Why not? It's a little tacky, but basically cute and harmless.

Maybe they have trouble finding their SUV amongst a sea of identical sort-of-pewter SUVs and need their unique family configuration (look! a straight couple, two kids, a dog and a cat!) to figure out which one just beeped back at their remote control.

Because people do dumb stuff.