Logically, this must generate less income than it costs to run, otherwise the people running it would make more money mining Litecoins themselves rather than selling the service to mine them.
We are also mining ourselves and now we want to grow more. In order to mine more and reduce our costs, we need users. It becomes cheaper to buy more hardware etc., hence we are providing this as a service.
In a gold rush, it's always best to be the one selling the shovels.