[thinkingemote]

Gwern gives his opinion (I'm inclined to agree but I really love the idea that it could be the reason!)

"The Toxoplasma literature is dogged by small effect sizes and associated pathologies like p-hacking, extensive confounding (in addition to the obvious reverse causation), poor replication (every study seemingly finding a Toxo correlation in something else), and lack of any clear mechanism for how Toxo could be doing anything in a primate species so evolutionarily distant from its rodent target. So, as entertaining as it would be if cat-lovers were being brainwashed by a mouse parasite futilely attempting to get them eaten by their pet cat, I doubt that any effect exists at all—much less that it is the explanation."