Air Asia — asking 250 bucks for seats

Flight i5-1825
Date - 23rd jan
Pnr - msgiqh

I am terribly disappointed with the service from the lady who was at the boarding pass counter. Was asked to pay 250 buck for taking seats in any other row except last row. After boarding i can see there are so many empty seats in so many rows.

I need an answer "why air asia is using such cheap tricks to earn more money." and "why do passenger need to face such last minute trouble."