It’s not a question of whether it’s common or not to have a Terms of Service in place. Instead, you should focus on the pros and cons of what may happen if you write the Terms of Service yourself. Perhaps you’ll save yourself a few bucks and perhaps you’ll never have any legal issues along the way.
However, you should ask yourself what could happen if you make a mistake. Keep in mind what the terms of service actually is—it defines the relationship between the app and the users. It may not sound like much, but it’s the rules by which both parties agree to move forward.
Having one in place helps prevent things like abuse, offers information about who owns rights to the content, how to terminate accounts, and limits liability. While the law may not require you to have one, a solid Terms of Service may help you avoid problems in the future.
For more information about why a TOS is useful check out my blog: