You might like to think that when you put out a web-based script for sale you hold a monopoly on who and who can install it. Not true. Even if you make the thing the easiest script ever installed, you will be dealing, not necessarily with newbies, but with people who aren't as technologically skilled as you. These people can type, work a web browser and navigate your interface, but they don't know how to setup a database, set permissions on files and so on, and don't care to. This is where you.