Hi A37575,
I agree that being aligned with, and astride the centre line is ideal.
However, with a large cross wind there are a few problems:
1) As soon as the alignment process starts, the aircraft will start tracking towards the down wind side of the runway. If touch down is not accomplished quickly, then it gets expensive.
2) So bank into wind needs to be applied to prevent drifting. We are limited by bank angle in case we scrape an outboard engine pod.
3) The swept wing produces lots of roll with yaw, which has to be counteracted with aileron. If the cross wind is close to maximum limits, then the ailerons may be close to saturation with the very large yaw (to align perfectly).
The landing gear is stressed to happily accept up to about 5 degs of drift on touch down.
So with big crosswinds, the compromise is to remove some of the drift (to within 5 degs of runway track), and hence apply less bank into wind (prevents pod scrape), and have less aileron cross control applied thus leaving more control available (in case it gusts.)