Air Asia — baggage management

Sir we family of 3 we flying to vietnam via bkk in airasia on 25 th midnight night. We know about the baggage limit of 7 kg and since we were family we did nit divide our luggage into 3 sets but we just had 2 cabin suitcase totalling to 17 kgs.
The stupid girl in the check in, made us divide our luggage into 3 parts, wasting time of passangers & increasing the frustration of others standing in the que.
If family of 3 are travelling n luggage is less than 7x3 kgs either in 1 luggage of 2 luggage, so wat?? Wats the logic here, we r confused cz in bkk we had the same 2 cabin bags of 20 kgs, they created no confusion & let us pass.
Wake up india.