People roaming an exhibition floor spend 2 seconds looking at your small early-stage startup booth. Conference organizers usually create space for a huge logo and a tag line that is not very visible. It would be better to rebalance that.
People don't yet know your brand or logo, so it won't help to attract attention ("ooh, let's check out the guys from [BRAND]"). Your objective is to turn the 2 seconds attention span into 10 seconds, which then hopefully is followed by a visit to the booth.
Below an example in a random Tweet I found. Not the fault of this startup, they just followed the format set by the conference.
Image via WikiPedia