BizDev people do have a function at hackathons
charlottehan.com
charlottehan.com
I have some good friends on the sales side of things and they invariably leave the office at 6 and do fun activities, go to the bar etc. They seem quite puzzled that I would turn down invitations to go out in favor of learning new skills and building cool stuff.
In a business that's all about building and shipping products no matter what it takes, and at an event that is about shipping products in a very short time, it is not surprising that a biz dev person would be seen as somewhat superfluous. I'm sure the engineers at the hackathon were quite happy to have her make a powerpoint and get some beers though.