It’s an usual mod for a road-bike, but the benefits are two-fold:
They’re adjustable, whereas stock handlebars are not. With these, you can move them down the fork leg and splay the bar angle out to a more horizontal degree. For me, I like to have slightly less acute an angle than the stock bars, making it easier to turn the bike (more leverage).
Cheap and fast to replace in the event of damage. The tube unbolts easily and can be replaced with spares. I don’t plan on exercising this benefit though
PJ: The princely sum of £60 on eBay
Oh Boris, also, the grips are grippier than stock, giving a better connection to the bike. You can feel more of what’s going on at the front.