Because she has had fantasy f***s with romance book cover models, some nouveau synth pop band member, and a teacher or three. My gran was as puritanical as a Mayflower original, we still caught her necking booze straight from a bottle. People are hypocrites. Just look at all the anti-gay legislators/preachers caught with young men. Duggar and his "protect the children!" clan and his crimes.
No-one should care what you do as long as it's legal and consenting.

Everyone you know has "simped" about something they would never share with anyone else. Trust me, the internet is overflowing full of much weirder shit than what you like. Grown men shitting themselves in diapers, paying tens of thousands for an adult sized nursery, with human adult sized cribs, rattles, and stuffies...

Everyone has a "thing" and most of them are not as tame as yours. You can't let it bother you.