Why do more powerful programming languages tend to have slower implementations?
This is simply not true. And part of why it's false is that the premise isn't well formed.
There is no such thing as a fast or slow language. The expressive power of a language is purely a function of its semantics. It is independent of any particular implementation.
You can talk about the performance of code generated by GCC, or about the performance of the CPython interpreter. But these are specific implementations of the language. You could write a very slow C compiler, and you can write Python interpreters that are quite fast (like PyPy).
So the answer to the question of &quot;is more power necessarily slower&quot; is no, purely because you or I can go write a slow C compiler, that has the same expressive power as GCC, but that is slower than Python.
The real question is &quot;why do more powerful languages tend to have slower implementations.&quot; The reason is that, if you're considering the C vs Python, the difference in power is abstraction. When you do something in Python, there is a lot more that is implicit that is happening behind the scenes. More stuff to do means more time.
But there's also lots of social elements at play. People who need high performance choose low level languages, so they have fine grained control of what the machine is doing. This has led to the idea that low level languages are faster. But for most people, writing in C vs Python will have pretty comparable performance, because most applications don't require that you eke out every last millisecond. This is particularly true when you consider the extra checks that are manually added to program defensively in C. So just because lots of specialists have built fast things in C and C++ doesn't mean they're faster for everything.
Finally, some languages have zero cost abstraction. Rust does this, using a type system to ensure memory safety without needing runtime garbage collection. And Go has garbage collection, but it's so fast that you get performance on par with C while still getting extra power.
The TLDR is that more powerful languages are sometimes faster in some cases, but this is not a firm rule, and there are exceptions and complications.