I am surprised as to why people trade on yobit; it is a very shady one; yet people never learn.
Its been a forgotten exchange but seem to have gotten users up to this moment. Its just that these new users discover it today. I think most exchanges can manipulate prices, its just there we can't provide proof to it. Shady but the exchagne survive to be one of the top exchange still, they do have a bad reputation for holding altcoins upon withdrawal.
it is always a matter of convenience. some people in some countries (for example India these days) don't have that many options. additionally it is about them not asking for any kind of KYC and with btc-e gone they become some sort of refuge for those who didn't want any kind of KYC enforced on them. additionally there are certain shitcoins there that can not be found anywhere else. so obviously people tend to go there.