It's not reasonable to expect cabin crew to stow everyones hand baggage. Ideally you should only take what you can safely lift above your head.
If each CC member lifts 10 bags weighing 9 kilos on each flight they will injure themselves. You may not think that 9 kilos is a lot, but lifting bags on an aircraft is not the same as doing it at home, you are in a confined space and you are lifting in way which is much likely to cause injury.