There is this idea of built vs bought.
Cars
In car culture, it evokes the pride of building a car for a task rather than purchasing one.
The idea that the person who works on their car, researches parts, tests things out, and builds things is different than the person who goes out and buys a pre-built car.
Even if the pre-built car is faster, it feels like they kind of missed 'the point.'
Bicycles
For close to a decade I rode an old steel frame bike that was more than 30 years old when I bought it. It was 'too small'. But I rode that thing everyday.
I rode it on weekends all day.
It was my transportation, my entertainment, and probably my most expensive possession besides my laptop.
I did things with that bike that people thought were crazy. Sure I realized that some people were much faster than me. But I realized that my body system, my cardio system, was really strong.
I was being held back by the bike. In terms of fitness. And skill at descent. But if there was an objective measure of strength, I knew I was stronger than a lot of riders out there.
But the thing is, so what?
External comparison is fraught with pitfalls.
Skills and knowledge
Skills and knowledge would be two fo the key differentiators between buying and building yourself.
There is also the idea of goals. If your goal is to be the best racer, maybe knowing how to build a car is useful. But there is also a lot of racing specific skill that you would need.