Without boring you with the list I totted up 23 items I need to carry on my bike / in pockets.
Wow. I hope you don't mind me saying that I think you've overcomplicated it. I think I've four: keys, bag, clips and mitts or gloves. Sometimes I carry others, such as food/drink, the video camera or stuff I'm taking to deliver, but that's want more than need. The stuff in the bag occasionally changes by season but not by bike (the right tubes and magic links stay with the bike, as mentioned earlier).
Another view would be this. A bike is a form of transport as is a car - both cease to function adequately after a puncture. Would it be sensible or reasonable to keep the spare wheel, jack, wheel locking nut, wheel nut spanner for the car in the house and take them out for every trip? I guess most people would say no. It’s thought perfectly reasonable to leave the necessary items to fix a puncture in the car at all times.
I carry a bag, mitts or gloves and even more keys out to the car too (the bike keys are on my house keyring, but the car key isn't because IMO it's too flaming expensive to risk losing when not needed).
I don't think most drivers give a moment's thought to car repair toolkits and how crap most of the bundled ones are. They're only there because they were sold with the car. It's only oddballs (like relatives of car mechanics like me) that bother to test them before they're needed and replace the crap bits with usable tools, isn't it? Heck, I bet a fair number of drivers don't even know for sure where the keys for their locking wheelnuts are.
So if it’s reasonable to keep a car spare wheel in the vehicle why is it so difficult to understand why some cyclists chose to keep all the appropriate equipment to fix a puncture on their bike at all times?
That seems like a false equivalence. Even a pretty comprehensive multi-bike toolkit is maybe 400g - could be about 250g if your bikes don't include vintage/retro. A car spare wheel weighs over 10kg, possibly much more depending on model. One's clearly easy to carry and the other not.
Removing the items from the car or bike exposes the user to preventable risk. Perfectly logical to take action by leaving them in the car or on the bike to avoid this.
Leaving items in/on each vehicle exposes the user to avoidable cost and/or the risk of second-choice tools that fail when attempting a roadside repair. When I've had a car and van (for short periods, admittedly) the repair toolbox has moved between them and that seemed perfectly logical to me.
I guess we're each picking our preferred way to reduce the risk of being left with no useful tools.