If you are really performance concerned, you wouldn't use Python to begin with.
That said, there are many use cases where performance does not matter as long as it is not "too much", for different values of "too much" depending on context.
That said, there are many use cases where performance does not matter as long as it is not "too much", for different values of "too much" depending on context.
Your typical assembly programmer may be far more aware of their obligation to do so than your typical Python programmer, so in my mind it's more important that languages occupying Python's ecological niche behave predictably. It can be challenging to balance that need against other constraints like limiting the number of abstractions someone needs to master in order to be productive.
Sometimes raw performance does save developer time, because you don't have to worry that much about algorithm. :)