Also not sure why it is considered a particular hassle
APU on (at most places I will be doing that anyway) - so 1 extra button push (yellow hyd pump on) is all that is required. And that is only because the ptu is noisy and kepping yellow pressure prevents it from kicking in - but if you forget it isn't a major problem.
Even if you only save 15kg on a short taxi imagine if every 'bus operator saved that on every sector every day - no more complaining about it being hot in April!
(And factor in brake wear if you are light - someone told me that every time you apply ceramic brakes it costs about £5 in wear! Wasn't on airbus but that could really add up!).