I am surprised at your attitude!
People with "invisible" disabilities are just as disabled [and covered by the ADA] as those who ride in scooters or wheelchairs!
My husband has MS. When it was in its early stages, he did not use an assistive devices. But he had a handicapped parking placard & used the spaces. Why? Because he got tired very easily. He didn't have the strength to walk from the far end of the mall parking lot.
Now he is in a wheelchair - he no longer walks at all.
But he understands, whenever he sees a person who doesn't appear handicapped parking in one of those blue spaces, that it very likely is a person with an invisible handicap!
There are plenty of other instances where you'd be so wrong to criticize ...
For instance, when my husband and I go shopping at the mall, often I am overwhelmed with all the packages -- he can't carry any.
So I'll run out to the van and throw them in the truck.
If you saw me - obviously able-bodied, throwing packages into my van parked in a blue space - would you yell at me???
As far as handicap-accessible rooms on cruise ships, we have been closed out of several cruises because those rooms are booked ... and I have to hope that those who booked the rooms truly needed them.
From what I've seen posted on some message boards, people try to book those rooms b/c they are big -- and for no other reason.
Now that's wrong!