I like that a web app requires little commitment from users. They just visit the page and start using it. They don't need to download anything they might not trust, nor do they have to install it.
I've started a project related to video processing. It takes videos and returns a modified version as a result. It wouldn't make a very practical web app (users would have to upload the video, wait for it to process, then download the result, incurring extra waiting time for the upload/download and cost to me for bandwidth and server CPU usage), but I like that it would be "modern".
Am I being foolish? Are desktop apps not dead? Can anyone speak from experience how people respond to downloading a tool from someone they've never heard of?