Any reason you could think of?
Once my sister and I were not invited to a family friend's daughter's wedding. We had been invited to all the others and there were 9 kids in that family. My parents and another sister went. No one wanted to say anything. Months later we realized they sent the invitations to the wrong city because we ended up receiving them. All felt bad. That was dumb because these were very good friends of my parents and I can't believe my mom didn't ask.
Could that have happened to you?
When my son got married we invited everyone. Literally. Everyone we thought would come, did. But it was wonderful.