I don't think it's the question of gamers not respecting the sponsors, but the sponsor (you in this case) not advertising the event properly.
If there was sufficient hype and media around it you would certainly get more people entering it. Free shit is always good...
I didn't read about it on mygaming forums or the news team or www.langames.co.za and I suspect you expected people to just read your home page with the news announcement...
How many people went to the LAN event? 1? 2? An announcement at the LAN would probably have received a few entries at least...