Couscous on Tuesdays

I have another shocking confession to make. I really like Couscous.
Now Couscous being a traditional Morrocan or Tunisian food it is quite easy to find decent (Kosher) Couscous places in Beer Sheva.
The interesting thing is that most of these places, and almost all of the good places serve Couscous mainly on Tuesdays.
I know it is traditional to eat Couscous on Tuesdays (and Friday night, but obviously not Kosher places...)
However, one would think that there would be an economic oportunity here, that some people migt like Couscous on Sunday for instance..
But for some reason this is not happening.
I think this is yet another evidence that economic is inextricably tied to culture, and that cultural traditions sometimes change very slowly despite of economic incentives.