Selling copies to people who want it is more efficient than the crowdfunding approach: the people get their maps right away, and the author gets money right away. There's less friction in this approach.
Of course, we don't get the source code, which is a loss to some people, but all that extra "friction" involved in the crowdfunding path is why simply selling stuff directly is an easier way to make money. It also requires less guesswork on the part of the author as to how much they may be able to extract from the work, in total.
Of course, we don't get the source code, which is a loss to some people, but all that extra "friction" involved in the crowdfunding path is why simply selling stuff directly is an easier way to make money. It also requires less guesswork on the part of the author as to how much they may be able to extract from the work, in total.