I, personally, see it as a backwards business model. You pay for something unfinished, but not for a properly polished product?
Some creators throw in extra bits in appreciation for those that purchased EA stuff, fiesta's Nuova Bolide comes to mind with him throwing in a bonus for those that bought it. I mean frankly, if I have a few extra bucks to spend, and don't really need it for more important stuff, so why not indulge a bit?