However, the trick is to book early.
Cruise lines, for example, can accommodate disabled passengers, but they may have a limited number of wheelchair-accessible spots on shore excursions, and those spots fill up early. That's also true of land accommodations. If you want to go to Rome and want to stay near the Pantheon there are hotels that can accommodate people in wheelchairs, but each has a maximum of two accessible rooms. If you book early enough, there's plenty of opportunity. But if you wait, there's no room.
Airlines are very accommodating to people in wheelchairs and those that need help.