I think this is merely cost saving disguised as pro-environmental measure. They could always move from plastic bottles to US style "boxed water" if they worry so much about plastic. Otherwise, leave our water bottles alone or if you want to move to big bottles and glasses, ensure at least one water run every hour (so 1 run for <59 minutes flight time, 2 runs for 60-119 minutes, 3 runs for 120-179 minutes etc).