One important reason is the ease of delivery. If you're selling a desktop app you either need to build for different platforms (like JetBrains do), or limit you

One important reason is the ease of delivery. If you're selling a desktop app you either need to build for different platforms (like JetBrains do), or limit yourself to a single platform (as attested by the many MacOS-only or Windows-only tools). Additionally, you need to support mechanisms for remote updates, and even with that there are many customers who fail to update for various reasons, so you need to support old versions. With SaaS, you have full control over your product, at the cost of being limited to the in-browser (and mobile) front-end. Your backend can be written in any technology you want, and you can release new updates with any cadence you want, even continuously. And you can even replace the whole backend overnight, with your users being none the wiser (assuming it has full feature parity with the old one).