Early tumble dryers were often matched with automatic washing machines that had relatively low final extraction, and or worse, semi automatic washers like wringers. Either way you ended up with laundry that could be rather if not comparatively sopping wet.
High heat allowed these early dryers to bake all that water out of washing quickly. This was important I suppose to housewives doing more than one load of wash per day and wanted to get things over with.
For many years laundromat dryers in USA ran rather hot also because in part top or even front loaders didn't have the high speed final extraction found today.
To avoid customers backed up there is usually a fixed ratio between washers and dryers for laundromats. This of course goes out the window when customers either pay for far more time than a load needs to dry, thus tying up a machine for longer than it should. That and or leaving the place with load in dryer and not returning until some time after it has stopped. For the latter don't be surprised if wash has been removed from dryer, put in cart and shoved off to the side somewhere.