They should have never been granted the trademark based on prioriry. They did not coin or use the term first. They are not fighting because they know they wouldn’t survive a challenge which is why they just bullied small shops who themselves didn’t have the pockets to defend themselves.
I don’t think that’s what happened? Based on this article and another one I read, it seems that now the Taco Tuesday trademark is relinquished meaning anyone can use it. I’m guessing taco bell would rather everyone be able to use it including them rather than it being locked down by someone who’s not them.
Indeed that was the case:
According to The Strange History of Taco Tuesday, the promotional phrase was started in 1982 by a chain called Taco John’s based out of Cheyenne, Wyoming. In fact, Taco John’s placed a registered trademark on the phrase in 1989 to attach it to their brand. They filed a lawsuit against another restaurant chain after seeing that it was used, but the lawsuit resulted in bad press, so they have stopped enforcing their trademark. They still use it as their brand’s signature, and rightfully so!
https://bennystacos.com/taco-tuesday-legendary-tradition/
So Taco John gave up the trademark and now any restaurant can advertise “Taco Tuesday” specials.
