It's important to remember that the vast number of these will do and aim to supply little more than a few £ for their pocket and wont' likely sell to people from far outside their friends circle anyway. They'll charge little, deliver little, but will service the very cheap end of the market which is hard or impossible for a regular photography company to service whilst retaining a healthy working business (massive chainstore type setups might be able to service the ultra cheap with the photobooths and the like, but that is quite beyond your average photography company to go down that path).
Plus remember just because someone has a website and a "pay me" button does not mean that they earn anything off it.