Until now because once they have gathered enough profit then they would just deactivate the cloud mining so that the users who have thought earned something cant get their proposed plan at the beginning of their mining.
Services that happen to shut down at some point don't do that because they have gathered enough money, but just because of the fact that they notice a massive decline in new money flowing into their service. As long as new money comes in, these services will constantly be able to pay people what is being promised, but as I said, if the money isn't coming in, then they have no other option than to shut down an run. It's not for nothing that Genesis Mining has been able to stay operational for quite some time now -> excellent marketing is the main reason, followed by noobs vouching for GM like imbeciles, etc. For 'fun', let no one invest even a single satoshi in GM for one or two months, look at how soon they will shut down their service.
