I never had an opportunity to go to Disneyland as a young child. My first time was 13. I went several times with and with out family during my teens. I pretty sure as a teen I may have left people with un-magical moments from my antics. During my teens going with my GF at the time, having some college age group making us sick from passing some nasty gas, in the que to a ride, probably help make people think not families with out kids should be banded. Going with my future wife in our twenties, I did notice a stigma being kidless. When random characters used to walk around the place, and people would not line up but create a rough who goes first, and one group per side. I found in my old pictures that the character would favor looking at the kids side of the photo is we were sharing the character. If we were waiting for our turn, they usually waved the kids over first. The first time we made money for a trip as a family my daughter was 10, and I swear characters would pose with us more than with out her.
To those who think the kidless are ruining or making the parks more crowded, I think the kidless already have a disadvantage for not having kids with them. I am not saying that they are ignored. Maybe it is just me, but I feel those with kids get better better preferential treatment than those who do not.