Rhythm Thief said:
Some of us are inveterate fiddlers.

I learned how to maintain my bikes by pulling them to bits and putting them back together from an early age. When I moved on to cars I did the same with them: my first engine rebuild wasdone with no prior knowledge of how to strip and repair an engine whatever. The first time I did it, it all went horribly wrong, but that merely meant that the second time I did it, I got it right. It's how you learn.
I am some sort of a fiddler, but on a small scale otherwise I would never have learned even the limited maintenance I have up to now. It's a similar thing with cars. I'm just offering up an explanation as to why people don't do it. I'm not really that good at bike maintenance at all but I just know when something is wrong with it and where it is, which is still an all right skill to have. I've learnt what these bits are called now and how they work, I just can't do very much about it. Also things like screwdrivers, allen keys, and various cycle specific stuff is seen as expensive tools. I still see it like that even now.
I know quite a few people the same, some of it is how you were brought up my father is technically incompetent with any tool and some of it is when you have one bike it's viewed as more precious when you first get it, you daren't break it

. After a while you get more bikes and that all changes but by then you can't be arsed to learn as much new things along those lines

. If you apply how I felt about things and then put in even less effort and even less curiosity it's not really totally surprising that so many people can't/won't change a tyre. Well to me anyway. It's exactly the same sort of thing really for getting people to start cycling, they look on with horror at something costing £500.