There is a direct correlation between the proficiency expressed in mastering (or failing) mathematics as a subject; be it even in informal contexts, and IQ.
Assuming your premise is correct, bragging that one has failed at understanding mathematics can be equivaled with bragging that they have a low IQ...
Why would society tolerate and cherish this kind of behaviour? Well, because it fits the narrative, that is why. Humans manifest a herd-like mentality, especially those who are intellectually impaired; given their situation, they find understanding amongst those in similar situations to them, and thus create this cult of idiocy. If there are enough idiots to follow this cult of idiocy it slowly creeps into normality and all those who defy this new founded normality will be shunned.
TL;DR - bad at maths, low IQ -> low IQ, idiot