Originally Posted by menschmaschine
I don't know, but have some theories:
Bottled beer usually has more alcohol than draft. Does they do this for longer shelf-life?
Maybe. But I think this is to make it sessionable. A lot of British ales are made lower alcohol for pub drinking, where you'd want a bunch. Bottled beers are intended for more contemplative drinking.
In the US, this falls apart a bit because of the lack of a pub culture, and because the microbrew cult of high ABV. But it still exists somewhat; bars don't want you to sip, they want you to guzzle.