This does happen and tends to create competition. If your entire service is a very thin wrapper around a smart contract, the market may decide that a fork with

This does happen and tends to create competition. If your entire service is a very thin wrapper around a smart contract, the market may decide that a fork with equivalent functionality and lower fees is more worth using. On the other hand, if your service also provides other features on top of the contract (web/native interfaces, UX, hosting, ongoing development, customer support, and so on) then it may be hard to build a competitor simply by forking the underlying contract.