It really isn't.
> If you can build your own hammer in less time than it takes to drive to the store and back
You can't and your analogy doesn't hold. I've been writing JS frameworks work a decade, as have millions of other developers. They don't "drive to the store", they install their tool of choice in one second. You either build and maintain yours for hours or you copy paste code (which equates to the same).
> people irrationally fear not using frameworks for things not measured.
It is very easy to measure the hours spent.
How would you know? You are choosing conventions over measures. If you measure nothing you have no idea what is faster or not. I have been doing this work for nearly 20 years and many JavaScript developers claim measuring things is easy, but they never do it. When pressed on it they never have and don't know how. Instead they guess at performance to reinforce their own preferences. I have an autistic kiddo that does this and everybody sees right through it.
Because I worked in the industry when we all used jquery and I see the difference in real billable hours to nowadays. The entire industry has measured and shifted. Do you think million- and billion dollar companys shifted towards public shared framework for funsies and parties?
No. I don't have to hire an engineer and teach him our company bespoke framework. I can hire a react developer and he's productive from week one.