why must I be 18 or older?

From the Rover TOS:

1. Age Restrictions on Use of the Site or Services The Site and the Services are not directed towards children, and we do not seek to collect personal information or market any products or services to any person less than eighteen (18) years of age. By registering to use our Services, you certify that you are 18 years of age or older. Children under the age of 18 may not register or otherwise use the Site or Services, and parents or legal guardians may not agree to these Terms on their behalf. If you are a resident of a state that imposes additional or different age requirements for disclosure of personally–identifiable information, by registering for our Services, you hereby represent that your creation of an account, the provision of your personally- identifiable information to us, and our use of such personally– identifiable information as stated in our Privacy Policy, does not violate the applicable laws or regulations of such state.

Through some googling, it appears that in many states the minimum age at which one can be hired as an independent contractor (which is our status with Rover) is 18. Beyond that, child labor laws limit the amount of hours minors can receive per week as well as which hours they are allowed to work, which can vary from day to day and state to state. This would be a legal rats nest to enforce in an industry where we are providing services around the clock.