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.