Zero edge in standard casino games can potentially waste players time if you are forever at zero profit/loss long term, at least when you lose your money to a casino you can get on and do something else with your life ha, ironic.
Zero edge doesnt mean that player wont be losing or winning while gambling.. In shorter means than it could be refer as a simple math statistic that shows how much a site will earn through the wagered value or how many percentage that you lost for everytime you bet.
Playing as a gambler on a site with zero edge could be more profitable than a house with edge but still it is not a guarantee that someone will not lose to the house. On the other hand however, it is pointless to build a site with zero house edge since people are making gamble sites to earn something, thus having some edge is important to sustain the site