[shantanubala]

Only 37Signals is a B2B company that has a lot of customers that are developers. They have an API. Their source of income is their subscription and not apps for native platforms.

In other words, many of their customers who want a native app can scratch their own itch pretty easily, and 37Signals can cut down their own development efforts and focus on making their platform better.

The reason Evernote has apps for every platform is simple: that's the only thing they have going for them. Their interface isn't the best, and there are tons of other ways to save notes. They just happen to have really good cross-device integration. Other note-taking tools have users for different reasons.

I agree with 37Signals. App Stores are an obsolete concept that are only making a comeback because we have a new wave of devices without a solid set of mature cross-platform development tools.

EDIT: In other words, 37Signals wants to differentiate themselves from other applications in more unique ways than just "works natively on every device."