The cloning and piracy problem will always be there in one form or another, it is unavoidable. There are clever and sensible ways around this though.
Restrictive DRM that install horribly invasive software similar to viruses on people's computing machines does nobody any favours and annoys legit users without really stopping piracy. Some software (eg Adobe) and music (eg Spotify) companies have moved to subscription models recently.
I guess with 3D printing model files you could set something up like Spotify for 3D printing - you can print as much as you like for €20 a month but the software downloads the G-Code for your specific printer and print parameters rather than the 3D model file itself. So the slicing is done on the server, the user never gets the source 3D model file.