I don't know if I'm just unlucky, but most of the (Seattle) startups I know have a heavy drinking culture, and have alcohol at the office, so it's literally true, and perhaps used as a proxy for "will this person regularly stay late at the office (because they want to drink, and will end up doing extra work, too)".
This seems to be quite hit and miss when I've looked around at work cultures in Seattle, free beer at work correlating with working much past 4pm is a weak sign at best.