The truth behind this is just sadly... Well.. Truthful.
I'm not meaning to sound like a "fat shamer," even though I totally will come across that way. I know that there are lots of people with medical issues who can't change their weight... But there are a SOOO many more large people who CAN change their weight if they eat right and work out. The amount of electric scooters + fat people at Disney during my last trip was really REALLY sad. There was actually a LINE for handicap people sometimes. ALL the spaces at Fantasmic were filled with numbers and numbers of fat people who just didn't want to get up out of their scooters... And it's really sad for those who ACTUALLY have medical problems regarding weight/physical conditions.
Not attacking the OP at ALL. I'm just saying. At EPCOT, we LITERALLY saw an electric scooter GROUP of 4 fat people in about their mid 40s-ish.
Seriously. The stereotypical fat American tourist on electric scooters on film and TV shows exist for a reason. They're TRUE. And it's sad. So when fat people (WITH NO SERIOUS MEDICAL CONDITION) complain about not being able to ride things like Avatar, Harry Potter, or any ride that can be affected by weight due to their vehicles... Literally.. you wanna ride it? Get control of your life. Start a diet.
Sorry to all whom I have offended. But hey, I'm in college. I have a roommate named Justin. He weighed over 240 pounds when I first met him last year. I took him to Carowinds a while back (nothing but roller coasters) and he couldn't ride ANYthing but the drop tower due to his weight. He got tired of being called the "fat kid" so he started a diet and started working out... He weighs 185 pounds now and he's looking so much better than he originally did! So if you're fat and you're upset that you can't ride rides, either make a change or move on.
Sorry. I know I offended many. But somebody's gotta say the hard mean truth of it all. America runs on McDonald's. Woo.
Lets keep feeding it so one day it will grow to be big and strong. Theres no way Disney can build a ride seat that will fit every human. If you look around on the internet full grown adults range from 1 foot 10 inches to 8 foot 11 inches in height and from 4.7 to 1,400lbs. The best you can do is look for some happy mean range.