1. They’re easy to conceptualize. When you tell people you built an app for note-taking, they know what you mean. 2. They’re easy to build. Getting from 90%~10

1. They’re easy to conceptualize. When you tell people you built an app for note-taking, they know what you mean. 2. They’re easy to build. Getting from 90%~100% isn’t much harder than getting from 80%~90%, unless almost all real-world apps. 3. Everybody has an opinion about a tweak to the general formula that would make a better to-do app (for them personally). 4. They’ve seen others do it.