I agree that the level of service received and offered in shops and other business is partly a reflection of how expensive the goods/service offered is, not the wealthiest of the individual customer.
In an expensive hotel or shop or restaurant, people are indeed paying for extra service and the business expects to provide it. This could be that an expensive hotel turns back the bed in the evening, changes the sheets on a daily basis, offers quality room service and laundry facilities, or a shop offers a delivery service, or the staff will suggest other items to go with those tried on, or offer an adjustment service, or indeed pick the items up from the floor or seat in the changing room and put them back on hangers.
Customers receive this service and are not rude or entitled for doing so. Of course, they should respect the shop staff and treat them well and politely and not as slaves.....and the fact the staff carry out the tasks mentioned above, does not in any way mean they are belittled or demeaned - it is all part of the expectation of their job, and it should be remembered that perhaps they only deal with 5 or 6 customers a day and are t having to do all this stuff for the thousands at might go into a Primark dressing room each day - it is entirely different.
But for most shops, the high street shops, where a shop assistant might stand by perhaps 20 or 30 changing rooms which are full most of the time and where there is often a queue, of course the expectation of service is different and has to be different. Those shop staff, just like those in high end stores deserve respect and being treated decently - so putting clothes on hangers to help them out, is both polite and showing awareness of them and the difficulties of their job in dealing with hundreds of people.
Sadly, in customer facing roles, staff do face rude people. There are rude, demanding people in high end stores and rude demanding people in the cheapest of shops. The rudeness might take different forms. In the high end store it could be diva-ish behaviour, and treating staff as slaves and dirt. In your more standard store, it might be throwing massive piles of tangled clothes at staff, or rudeness, and treating staff as slaves and dirt. In either circumstance it's not okay. And in either circumstance, in most cases, the customer service response of staff needs to be to smile nicely and say nothing. The will be extreme cases where this might not be appropriate and there will be times when management should be informed and should be getting involved to support staff with difficult customers, but smiling and saying nothing is often the right response to low level customer rudeness - including not putting items on hangers in my view. Speaking rudely and sharply to customers, insisting they do things like putting clothes on hangers (very different to asking politely) isn't good customer service and rightly, isn't what stores want from their staff......even if customers haven't been as polite and respectful as they should be.