I give my side projects away for free because I have a $job to pay for the roof over my head, food, etc. and don't feel the need to make more money from my hobby work.
I create my side projects in the first place because I like to prove to myself that it is possible to do mad stuff in the browser - like a screen recorder with canvas composition, teleprompter, live annotations and talking-head overlay[1]. Or an SVG-inspired image filter builder for local batch application to images (still a WIP but almost there)[2].
It doesn't cost me any money to host the results, so: why not?