I kind of see it as what noble families did when they would have to many children. If you born in the 13th century and were a unplanned or unwanted pregnancy in a middle class or noble house your parents would give the church a payment and you be nun/monk from the day you were born. I don't see it fully in that light because the Inquisitor is 20+ years old. It is more like mommy and daddy are saying "Go help your cousins you'll love the Chantery/Templars".
Yeah, it's also important to remember that the idea of duty to one's family is probably much stronger in Thedas than in most modern developed countries - not just in terms of parents deciding marriage partners or whatever, but also the sense that every action you're doing is for the good of the family. I don't think there's often an option of pursuing independent interests, even for nobility.
The character bio sorta subverts this by saying that the Trevelyan noble can disagree with following their family into the Chantry's service, but ultimately we end up at the conference regardless.
(Where this would obviously most contrast with Dorian's story is that the Free Marches' attitudes to sexuality are probably relatively more open and pluralistic, and I don't think the nobles would be as obsessed with blood purity as the Pavus clan.)