It's also not the case that the tickets on these sites belong to fans who can't go and are hoping to sell on for a small profit, they only use 'registered sellers'.
This means that unfortunately there are possibly ST holders with no intention of attending any matches, the have a ticket purely for resale value.
There will also be people who had bought a membership and single match tickets again purely for resale. This is why I am glad City had moved to Mobile Download tickets as these are far more difficult to pass on than the Mobile Tickets sent in emails were.
I've actually bought from this site before (Villa 21/22) and was sent Mobile Ticket download link showing original owners name in the info section. If club was seriously about tackling touting they could quite easily find the names of who is selling on their tickets.