May be in the minority, but the ability to charge someone based on consumption (# of drinks) instead of hourly or by guest count would seem to be necessary.
If you are batching anything, you need to be able to make it spec'd to consumption totals since people can come back for seconds or thirds. Doing so would insulate you from any issues if someone wondered why you ran out when you made the equivalent of necessary drinks. This would be useful for Matcha Carts, Tap Carts, or even potentially espresso if you are charging based on consumption.
Seems like a no-brainer as most hotels/venues/catering charge on certain number of items especially when it comes to drinks unless it's an open bar concept (and even then sometimes they'll charge based on consumption - ringing up a $0 sale). And I do believe this is essential to ensure pricing is accurate for COGS purposes.