Trademarks are an asset to a business, and businesses protect their assets. It's not a matter of believing customers are stupid. It's a matter of ensuring that the names which identify your business are not used to either identify another business or used in a crude way that can harm your business and destroy the value of your assets. By aggressively defending even close imitations, they send the message not to attempt to co-opt their brand.

And in a world where people are going to ophthalmologists after having put sunscreen on their eyeballs to look at the eclipse in lieu of wearing eclipse glasses, you may be giving too much credit that everyone can tell In-n-Out Double Doubles from Smashburger Triple Doubles.