You don't need a contract to have obligations.

Example:  You hit a kid on a bike with your car while driving.  You are now obligated to pay for his medical bills.  No contract, but you have an obligation.

Example 2:  Someone leaves their purse under a park bench, which you find.  You are obligated to turn it in to the police or find the rightful owner.

Example 3:  Someone deposits $10,000 into your bank account instead of their own by mistake.  You are obligated to report the discrepancy to ensure the money gets back to the right person.

Everyone who supports this site is a scumbag in my book.