I think it's people buying into the tale that Gemporia is one big happy family, and that the presenters are the viewers' friends. So there are plenty of people who will buy from certain presenters because they get mentioned in live shows. There is a woman who calls herself Mirabelle who seems to watch every show, and has done for years. She's always messaging in, and has sent in gifts for presenters.
I think there's also some people who like to buy to "help" presenters out. I have heard of viewers following presenters around the various selly telly companies, and buying anything from their early shows to help the presenter get settled in to their new job. And they don't see that as being a strange thing to do.
Plus it's shopping, and that's addictive. Especially when you have presenters telling you to "Fillbyour boots" and buy everything for one daily shipping charge. Some people are going to be in for a shock when they discover that Nan's spent their inheritance on coated jewels, plastic clothes and handbags, neon makeup, and overpriced health supplements.