Again we saw an exchange got hacked. There would be nothing to hack there if people didn't keep their coins on exchanges! For the love of Dog (lol), don't keep your coins on exchanges, start practicing safety, this is your investment we are talking about!
Following your logic, there would be no robberies at all, if people at all didn't possess any valuable things 
Maybe it's rather the problem of the exchange that did not take enough precautions to protect the people's savings?
I also assume that hack attacks could be successful because of leak of data from the owners of the exchange..