Isn't there a psychological aspect to this - that if you are on the cutting edge of languages/frameworks, that you believe you will have an edge over everyone else and a chance to be better for a period of time at least? This is of course typically ignores whether the cutting edge can actually solve problems better than mature languages/frameworks.
Psychology is a very broad area. We all want to be part of something, a community or culture, especially one witch is highly regarded among our peers.
Psychology or survival? How much demand is there for someone who's maintained an MFC app for the past 20 years?
This person could ROCK at C++, but who's going to look at his resume and give him an interview?
While I generally agree with you, I'm not sure Python is a new trend.
I had an opportunity to learn Python around 1996, and I passed. When I came across it again in 2003 I tried it, then kicked myself for not jumping on the bandwagon earlier.