To be fair, the applications of geometry that most people might end up using in real life are going to be boring to a 15 year old.

How many paving stones do I need to buy for the walkway I'm building in my backyard?

How far from the top of the roof should I start attaching this gutter so that I still have roof to nail it to 30 feet later?

How big of a ladder do I need to get to that branch I want to cut down in that tall tree?

Will I be able to get this couch up the stairs, around the corner, and through the door?