I think for people with mobility-issues it is. A lot of times, even with handicap placards, the handicap spots can be completely full. This was our experience when we visiting this summer. Luckily we had rented a scooter and a big enough SUV to get the ECV and us all in that my mom didn't have to walk to far to the gate (she has congestive heart failure).
Back in the day, when we had kids that we were renting strollers in the park, if we had to walk from the back-40 in without a tram, my kds would've been whining before we even hit security. Would've definitely put me in a mood before we even entered the parks.
I won't even mention having to walk back to your car at the end of the day, especially if your waaaaaaay out there (and add a sudden rain squall that pops up as well). The trams help and do add a little bit of convenience (and a bit of magic to start and end your day).