sometimes the pt's and gym instructors sorta have to give shit machine workouts to people. usually the untrained, elderly or female.
unless the trainer will be there for all the session, he cant prescribe squats, benches and deadlifts to some mother, or 50 yr old, or overweight dude. they will have bad form, not use enough weight, feel uncomfortable(and probably stop coming), be confused etc.
i know its not the best thing for them but its better than nothing. after 4-8 weeks of lat pull down and leg press the client will have the hang of pushing themselves, body awareness and see the benefit to Resistance training and then you can prescribe deads, squats etc. its not right but sometimes you don't have much choice.
but pt's who training their clients using only machines all the time are lazy retards, who don't know the power of resistance training.
you also have to remember that we all enjoy working out, we're lucky that we love to do something that is so beneficial to us.
biggest mistake beginners make - not using enough effort
What did all those people you describe do before PT's?
I know, we didnt have fat lazy people back then, beause we all squatted, deadlifted and pressed.
The reason they keep them on by giving them useless exercise is for the dollar, its a business first, doesnt matter if the client isnt improving, just tell them they are.