Coat Hook On Jetliner [VIDEO]

I took a flight on a Canadian jetliner, and they had coat hooks built into the seats.

I have taken dozens of flights, and never before have I noticed one of these. Are they common? The aircraft was built in 2003, in Canada (where, I assume, coats are worn more often than in the lower parts of North America.

Have you ever seen one of these on an aircraft?