Maybe with a big enough garage and a lot of hours, and donated parts, they could build a half-dozen cars to that same spec. Because programs are digital, and digital things can be copied as many times as you want without losing any quality, and because the Internet makes it possible to move digital copies at almost no cost, everyone in the world who wants it can have a copy of that program. And that's happening in more and more areas of software. Because the more people get on the Internet, the more they can hook up with others of similar interests, and the more likely it is that someone, somewhere, will be making the kind of program you need or want. Sometimes they'll want to sell it.
Some shareware is strictly on the honor system.
Maybe they're idealistic about the freedom of information. Maybe they just hope to get a little famous for their magical programming skills. Whatever the reason, it doesn't hurt their use of the program for you to also have a copy. Naturally the corporations also hope to generate good will and sales of any related goods and services. That last is the big news in version 6.0, with lots of options for choosing your Internet radio music.