

A deadbolt is more secure than the lock on the doorknob, but both can be picked or broken. Lots of homes have both locks on the front door, and in a lot of areas just the doorknob lock is secure enough if you’re leaving for a couple hours in the middle of the day.
A deadbolt is great, but it’s easier to break a window than pick even a bad lock. If you don’t live in a neighborhood where everyone has bars over their windows, you probably don’t need to keep your deadbolt locked all the time.