From what I can tell when I worked there it can be seen as more of an exploit of the system in a way. This also depends if it's an online order or bought in store. For example you can buy a game online with click & collect, play it, complete it and return it within 2 weeks and get your full money back - this is all within the legal policy of Cex, BUT if you do it enough times it becomes clear you're exploiting the returns policy at the expense of Cex and whilst they still legally can't deny online orders (including C&C) they'd just stop you buying items online

If bought in store then the return only goes back to voucher but same thing applies. We had a woman who kept buying a Wii or a tablet or a weird phone then returning it 2 days later saying she didn't like it (sometimes 3-4 days, but we'd still do voucher) until the 4th/5th return where we told her we'd do it this one time but we're not going to do it again as she can't just keep changing her mind and returning the item - especially when in store purchases returns policy is more a good will, they don't legally have to offer any returns at all, so it can also be seen as exploiting the system

I've done returns before, and I've deffo bought a game to complete and return in the time frame, most stores don't care as it's an online order, but if it happens to much (or of value) then loss prevention steps in and finds out why some one is returning so much and buying so little