Crew members during a flight are not the passengers’ servants. Flight attendants know a lot more about the plane, the flight, and what’s going in general in the air than you can imagine. They are there to help travelers, but their job description is much longer than this one task.
The primary concern of pilots and their teams is safety. They have to know how to administer CPR, first aid, in-flight firefighting, defibrillation, emergency landing procedures, and security as well. Their jobs are not easy as they juggle multiple tasks only one of which is customer service.
Passengers’ main concern is whether the plane is going to crash. It looks like they should be more concerned about the blankets provided by the airline. Pilots are generally 20 minutes from an airport at all times.
Also, if your drink contains water, it most likely came from a place you don’t want. The potable water is filled into the same tank that distributes to all coffee pots, hot tea, and, yes, the lavatory sink.