I think the issue people have with "booth babes" is that it presupposes men will be the ones perusing the booths, or the ones whose attention is worth grabbing.

There's nothing wrong with valuing someone for their good looks, but in a field like tech where we are trying to encourage women to participate more, using BB's at tech events is a reflection of the event organizers choosing to cater only to men, since it's mostly men that the BB's will entice.