Do bear in mind that prior to about 1970 there were no seating reservations and all pax would sit where they chose. LCCs have just gone back to that.
Regarding "appropriate pax" in the exit rows (like me
) a CC member is allocated to stand at the overwings during boarding and will guide away any pax (eg with infants) attempting to sit there. When boarding is complete they will then give the exit row supplementary briefing. These rows are the most popular among LCC frequent flyer business travellers because of the extra legroom so often fill up first.