Why is the no to do app on iPhone?

Note pad can be used as a to do list, or you can use you calendar if its over days at a time

There are also several iPhone web apps for the purpose, as well as installable options if you want to hack/modify your iPhone.

I’ve read speculation suggesting that to do functionality was left out of the iPhone because Leopard will change the way OS X handles to do lists. Apple may add to do lists to the iPhone after Leopard comes out.

But yeah, it’s a big missing piece. My favorite to do lists for the iPhone are Ta Da Lists

http://discussions.apple.com/index.jspa