I concur, having advised many student organisations over the years in the US and UK. Often such events are supported by organisation funds raised in other ways, rather than as generating income. And many universities have a body of some kind that serves to advise and support student organisations (including administrative and events advice).

Finally, in many cases, students actually want to gain experience organising events, sometimes for personal development and other times just for CV fodder. Farming events out to an external company eliminates this possibility.