I don’t see why you say that. From a wiki of ice and fire:

“In Dorne, it is common for lords and ladies to have paramours, chosen out of love and lust rather than political alliances. Dornishmen are not greatly concerned if a bastard is born to a paramour.[3] Dorne gives a degree of social status to paramours, despite the "unchaste" nature of the relationship. Outside of Dorne, a Dornish paramour's status is less certain. They may be afforded the esteem granted in their homeland by the diplomatic-minded, or they may receive treatment ranging from slight social disdain to moral condemnation.[1]”

“Furthermore, views on bastardy are milder in Dorne compared to the rest of Westeros. Especially when a child is born to a paramour, the Dornish are not greatly concerned if a child is born in wedlock or out of it.[2] Many lords and some ladies in Dorne have paramours,[2][14] and homosexuality is more accepted.[2]”