At networking mixers I've attended, often there are a limited number of drink tickets per person and a set event duration. But the drink tickets only covered alcohol, not other beverages. In some cases, other beverages just weren't an option at all. ("I guess you could find a water fountain? But why?")

Also, one of those recurring events was hosted at a startup that was, to be frank, known for "worse than college" level planning all around...

Eventually events started getting better at providing options. Probably a mix of several factors: the move to another city (local culture), career growth/level of people around me, and changing social patterns. (increasing interest in non alcoholic options/ more people willing to speak up)