So is Valves community to blame or what
and plus how the forget does it affect WSGC?
Skins have value because you can sell them on the market for steam wallet money (There are sites that let you withdraw them as actual paypal funds iirc), but before the market was a thing people were trading TF2 items all the time, usually for keys I think. I dont know how TF2 trading worked back then
A few months ago there was an incident about how people running these sites were rigging the results, either for their sponsors or for themselves to win. Additionally people who owned these sites pretended that they didnt (i.e. Tmartn) to trick people into thinking they could win as easily as him. Once this was uncovered is when valve stepped in and closed a lot of sites. Dunno why the WSGC is involved, but I guess it was because of the rigging scandal and they wanted to prevent it as much as possible.
Why is it Valve's responsibility if they don't run the gambling sites?
My guess is to prevent more of these sites popping up. Cut off the head of the snake and the body will die, or whatever