Comment by lossolo

This is something I realized a long time ago when I was running specific site for a few years, we had some users that would abuse the system, there was a technical solution to this that would completely eliminate abuse but the systemic cost of implementing such a solution was just too high because it would affect the whole system in negative way. So you basically accept some amount of abuse/fraud/cheating until it starts to affect your business, this is optimal choice in most cases.