[quote:3k4bxmmf]Is that something it picked up from the prevalence of stout? The brewers were buying the stuff in vast quantities so they just bunged it into the ales as well?[/quote:3k4bxmmf]Possibly, it might have been used for colour adjustment too as you wouldn't need much to increase the colour compared to using extra crystal malt.
It could also explain why/if they use the same yeast for the stouts.