When you come to a networking meeting do you notice how others are dressed?
Look at it this way: If you were going to run a marathon, what would you think the chances of success would be if the person next to you was wearing a suit and tie, was wearing hard, black business shoes and was carrying a briefcase? You might question their sanity at the very least.
Might the same apply to how you dress when you come to a networking group? If you're there to network and perhaps get a referral for a potential interview, wouldn't it make sense to dress for the job at hand? After all, if our marathoner showed up at the next working meeting in his shorts and running gear how many referrals for a potential job interview do you think they'd get as compared to the person who came dressed in business attire? If for no other reason, this might be an excellent time to upgrade and modernize your wardrobe in preparation for the next interview.
And, like it or not, the job at hand is getting in front of potential employers, so it just makes sense to dress like you're ready to get down to work today.