* Cost. Weddings are more expensive than ever and including kids explodes the numbers for a lot of families. They can afford 100 people, they have 150 people expecting an invite, and making a decision like 'child-free' helps them work that out.
..and then add in the cost of the 'in-house babysitters' that some parents expect the bride and groom to foot the bill for...yeah. weddings are stupid expensive, and even tho Junior doesn't "really eat much adult food!" there's still a plate at a seat that has to be paid for. I didn't see an option for 'kids meals' when i was planning my wedding reception.
* Some parents do not handle their kids and that can lead to disaster. In that case, a whole wedding might go child-free over one cousin's children.
oh yeah. i mean - some parents just let their kids go free-range at weddings - i swear half the time parents aren't even keeping a tight eye on the kids because there are SO MANY ADULTS around, there's probably eyes on them all the time, right? (No, the answer here is always no.)