If the No Show is for a booked room or a seat over dinner, it has to be paid for, if it was not canceled in time. Every booking requires some preparation and/or stop sale action. If a venue or a hotel planned an income based on your booking, a No Show would be a loss for them, especially if it takes preparation such as preparing food or stopping the sales process for rooms.
If we have a big group for the accommodation of a buffet-style dinner, for example, hotels and venues usually tolerate a 10% decrease in the number of attendees.