Besides being a great tax write off (travel, meals, housing, etc..), attending a industry-related conference or conventions gets you out, away from work, away from routines and energy sucking tasks.  They put you into a new environment that suddenly stimulates your senses and invigorates the mind because you are now around other like-minded people

Meeting people who can become new contacts, new referrals who can open up new conversations you may never have had via internet, email or online discussions.