Why does everyone want to sue everyone these days?
Patents and copyright you can not enforce if you choose not to but trademarks are a different animal.
If you are successful but don't register, someone _will_ register it in the same industry and sue you for infringement. They'll also some times hijack your Amazon listings if you are a seller.
This is not legal advice, just my opinion.
And even then, that doesn't prevent a frivolous suit in the USA
This prevents established companies from being damaged by opponents registering their marks.