i view it as being cheaper than driving back to the city or town, paying a fortune in car parking fees
But the city/town has dozens of shops so you can try things on in all of them. Plus not everyone needs to spend a lot to access them. I am a couple of miles from two big retail parks and a big shopping centre. I can also get to a large city on the park and ride, which can cost as little as £1.50 on the bus.*
I can also make looking for and trying things on part of a day out and also visit some galleries/museums and go for lunch so even if I don't buy anything much, the day and money isn't wasted. Whereas you can spend a tenner or more on postage and returns and get nowhere in the quest for much needed new clothes unless you're lucky with fit etc.
I was looking at it from my perspective. My towns is dead. We don't have the big name shops, we have a small Primark and a small H and M. I'm in awe when i go the city and find these stores are over a couple of floors!!
It takes me 45 mins to get to the Trafford Centre if I want decent shops and an hour to Liverpool or Manchester. That is a big chunk of my day by the time I've parked up, wandered into the centre and found the shop and return home.
Shopping is something i don't enjoy so I would rather do it in my own home where I can see what an outfit would look like with different shoes, shape wear, etc.
Also if I'm on a day out doing galleries and museums I don't want to be carrying shopping around
For less than a price of a cup of coffee( usually) its worth it for me to order a couple of sizes and return the ones that don't fit. I save time and a decent amount of petrol money by ordering in line, so I dont have to out in the first place and then go out again and return stuff that is not right.
Like everything,It'll suit some people but not others.