What does python3 have to do with anything, let alone conflating cost and benefit under as "big deal" as if they were the same thing?

It seems to me that we change things all the time in the computer/software field, languages, platforms, UIs, OSs, etc. are always changing, often at great cost with dubious benefit. Python 3 is one example, Angular is another. I could list examples for days, literally.

Therefore, to me, the idea that changing the default branch name on GitHub entails great cost without tangible benefits is a non-starter.

I'd rather argue about Python 3.

Don't paint the whole field with such a broad brush. Yes, some people are happy to change anything and everything at any time for any (or no) reason. But don't assume that everyone's on board with that.

GitHub is on board with it.

Look, there are riots, burning looted building, people getting injured and killed, including police, and world-wide demonstrations. Two guys got lynched in California in this month.

Do you really want to approach this from a cost vs. benefit POV?