This seems to have only started happening since the 14/10 update - and I can’t find anything in the patch notes to suggest that auto re-queue was removed intentionally. I’m thinking, and hoping, this is a bug.
I like to read and watch things between games - and having to manual requeue is making me to an extra click I don’t wanna do.
The suggestions to have it as a check-able after your first match is a good idea imo.
Edit: “We are aware of an issue where auto-requeue for Quick Play is currently not working.”