the demo is a proof of progress, nothing more, nothing less. It's not intended as a marketing demo, akin to the ones that used to be provided for free. This is a game running completely off of donations.
If things still worked like the time period in mention (with free demos being a normal thing), many of these companies would not exist, and this game would not be an option. for anybody. Those were the days where without a AAA publisher to push your game, you had no chance of making it at all.