I have to agree, I've been to several weddings and the only time I've ever had to stop for food on the way home was three different weddings that were all canape/cocktail weddings.
There was a few reasons but the main ones were:
You're generally standing up a lot and moving about a lot at a cocktail wedding (as the food is mobile too). That means you're burning more energy than if you're sitting down. That equals more hungry!
15 different canapes might sound like a lot but not everyone is going to GET 15 canapes. I remember one wedding in particular where the servers barely got out of the kitchen before their platters were empty because there was a group of particularly hungry people standing right near the door. They'd take several each and the servers weren't getting around to many of the other guests.
By the time that particular group of about 15 people were full, the servers were on their few platters each meaning that there were many more polite guests who were lucky to get scraps.
People tend to drink at weddings which increases appetite. I suspect that was the biggest problem of the group that ate a large portion of the food at the previously mentioned wedding.
They were drinking, already hungry, and not interested in sharing lol.
So basically I've yet to attend a cocktail wedding where I haven't had to eat on the way home. I know it's not up to the people getting married to feed you, but I never want to eat on the way there in case I get there and there's a lot of food. I feel guilty if I don't eat knowing that the people have paid good money for the food!
I think if you have a later ceremony (say 2-3pm?) and then a cocktail reception that goes until 5pm then generally it's fine as people will eat before they arrive knowing that there won't be a 'meal' provided. But if you're having a standard timing wedding and expecting people to be there for a meal time and perhaps stay late then cocktail receptions generally aren't enough imo.