Too simple logo marks are not protected by copyright. Even if it is protected, only dead-copies that imitate the shape of the logo can be suspended. Granting copyright to similar logos that are "May be a little similar" would overly restrict the use of competitors' logos.
On the other hand, if the logo mark is registered as a trademark, the scope of its rights is relatively widely protected. Even logos in a similar range imitation that cannot be covered by copyright can be suspended if they are trademark rights.
Trademark rights do not occur without registration (paid), and copyrights occur (free of charge) at the time of creation, but that is not a very convenient story that rights are protected for free.