I think its more an issue of someones' pride and joy being duplicated and used without their consent. It doesn't really have nothing to do with money/support or anything else (well at least not for me), people put these modifications together for free and I guess it is annoying that someone else comes along and redistributes them without asking.
Like if you are giving sweets out to people then someone comes along takes a handful and starts giving them out to other people. Sure you don't
really mind but you'd rather have given out the sweets to the person yourself, would you not?