The reasons are as follows:

R is the abbreviation of REGISTER, which means registered trademark when used in trademarks. The circle R is the mark of "registered trademark", which means that the trademark has been registered in the State Trademark Office and has been examined and approved by the Trademark Office, and has become a registered trademark. R trademark has the characteristics of exclusiveness, exclusiveness and uniqueness, which belongs to the owner of the registered trademark and is protected by law. No enterprise or individual may use it without the permission or authorization of the owner of the registered trademark, otherwise it will bear the tort liability.