Possibly because Python is heavily used by very beginners or web developers.
Beginners don't know any different and probably think all languages die and a new one takes its place every few years.
Web developers are a pragmatic bunch. They don't dwell and just jump onto the latest tech that fulfils their contract.
But in general, yes I agree, I would be pretty nervous if C++ changed too much. This recent trend of async / lambda *everything* is a bit too much change for my liking but that is due to new features that some developers over-consume rather than deprecations. I think the worst we have is a few C functions have been deprecated but the preprocessor kind of solves that in a quick and dirty fashion.