I didn’t know there was a need to justify why we carry what we do. But here goes:
I have two bags – one tiny one which I only use for very short blasts and one large one, presumably of the type causing the OP such offence (but it was second-hand). I refuse to buy another. I generally ride alone, and (as above) will easily get through 3L of water on a decent ride. I carry links, chain splitter, first aid kit (yes I have had to use it), keys, phone, rain jacket/winter warmer jacket, food, pump and generally 4-5 tubes (before I went tubeless). I would usually use most of them on a ride. I don’t tend to change what I carry as I would only forget something in the rush to get out if I was constantly changing the contents to suit the ride.
Apologies OP, I’m not changing, I don’t like the very long tedious walks.