I agree Bitconnect has no value. But apparently there are some people that are willing to buy it. Perhaps they believe Bitconnect will make some sort of miracle comeback, honestly we will never know.
But about Bitconnect still being traded on exchanges, the answer is simple. Exchanges can't simply remove a coin/token instantly just because it became a scam. If exchanges remove these tokens so quickly, without at least a months' prior notice, they become the scammers instead because they are freezing customers' assets just because it shut down. Be it a scam or not, the exchange customers paid for this particular asset, and they should have the right to trade it as they wish.
If exchanges are going to delist Bitconnect, they will have to go through the process of informing their users weeks beforehand.