Systems language and web language are not just a different name for the same thing --like Voiture and Car.
And, no, that their function defined in abstract and in totally generic terms is the same, doesn't make them the same thing.
"move data from point A to point B" can be said for any programming language. As such, it's not particularly enlightening when comparing a language's suitability to a specific task.
Turing-completeness aside, your argument misses the point that a particular language's design, compiler, library, toolset, (heck, even a particular language's community) can make it better suited for system programming or for web programming or for some other field.
Avion: transport des personnes du point A au point B
Boot: Menschen bewegen von Punkt A nach Punkt B
We are talking past each other :) Here is your first comment interpreted through your second one. There is no reason to have different languages, but it's OK to have different jargon.
I might not get the joke. Do you mean this ironically?
There sure is reason to have different programming languages, and it's called specialization (see: necessary engineering compromises).
My first comment says: two objects having the same generic functionality, does not mean that one and the same object can implement their specific (non generic) functionalities.
My second comment says: the same thing, basically.
I mean that (programming) language is a special kind of object that has enough versatility to express any idea in a reasonable form. Historically, our programming languages weren't that good in versatility and made various utterances an universally agreed on pain. But we are getting better and there is no law in the universe saying that we'll be forever stuck in Babel.
To some extent, your point is that Shakespeare is better in English than in its German translation for style reasons. My point is that it doesn't really matter and that an universal language is better than Babel because of network effects. Life is too short to erect artificial communication barriers.
Boat: move people from point A to point B.