Perhaps it exudes pheromones? It can't hurt that it's purple and the school I work at has purple as one of its colors, but overall I think I'm going with the pheromones hypothesis until something better pops up.
ETA: In case anyone wants to know, it's a Joe Brown cardigan that I bought from Simply Be in 2013. I don't see that particular one on sale anymore, but there's others there, and Googling for "Joe Brown's clothing" will get you places that sell non-plus-size versions of the brand, although mostly in the UK. There's some on Amazon too. I'd describe the brand overall as sort of boho/funky.
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