I can't install software at work, so a web app would be the only to access my stuff during the work day. I also have a shared computer in my living room that I don't install personal apps or log into personal accounts on. Web apps let me quickly access something there when I need to and log out easily.
You are right. I basically build my apps for myself who always use the same computers. I understand there are various people with various needs - but I would like to focus on pleasing people who are similar to me. I believe this is important to provide a good service. I don't feel like making apps like Microsoft Office with tons of features to please everyone.
Internet-connected is the key term here, though. If your target audience are internet-less note takers, then a desktop app is the correct choice.