I've played in bands with several 'left-handed' guitar players who played 'right handed' guitars normally. They all claimed it's an advantsge because they use their 'best' hand to fret.

Also, watch a non-player playing 'air-guitar' (especially youngsters) - they instinctively have their 'best' hand 'fretting' and the other hand 'strumming'.

There are no left handed pianos, there's no need for left-handed guitars (IMHO).