So, why, sitting in a wheelchair, would DD and her companion also need or get front of the line speedier access? Good question and it seems to me that whether it is actually needed or justified depends on the individual's and perhaps family's situation.
Let's take DD's situation. She would pass out - even when sitting in the chair - when overheated, which happened when crowded among those who were standing. Also, she needed physical assistance to walk the step or two onto and off rides, so as not to fall. Certain seats were often designated for disabled access, so the ride operators and assistants needed to organize who would sit where, which they could better do if those needing assistance were up front. Many rides had steps or other tricky access, which necessitated a special entrance for those who couldn't navigate same.
All that being said, probably half the time, she/we did not go to the front of the line. We waited with others, until the ride operator or assistant saw us getting close to the front, and then determined whether we would move up OR back a few spaces so as to be efficiently organized into the appropriate entrance or seats. In a few situations, where the crowding of lines seemed to be leading to dizziness etc, we either asked to leave the queue or asked if we might be able to get into a disabled access seat sooner.
So in our case, front of the line was needed only sometimes. It was granted whenever needed, and sometimes when not, and often to help staff efficiently shuttle people onto the rides.
PS - we were there over New Years, and navigating the crowds was extremely difficult and at times claustrophobic.
PPS - we stayed far away from the most popular "thrill" rides, opting only for the relatively less crowded tame experiences.
PPPS - I live in PA and have a disability placard. I appear to walk relatively well. However, if I parked farther out in the lot, The extra walking would become difficult, and i would soon be obviously slower and limping and need support. I use nearby parking spots whenever possible, and avoid taking up handicapped spots that others may need more than I, Unless they are the only close spots.