It's not as if they started as a "family" of languages, each one of those was just one discrete language at one point.
There's no way Wolfram can succeed with its much more complex feature set without a spec and a reference implementation that's not closed source. Flash pulled that because they caught that opportunity window in the browsed, but neither CDF as a format nor Wolfram (Mathematica language) stand a chance as a generic language. Even Matlab stays niche.
R6RS completely failed to establish itself, to this day R5RS is more popular.
You'd be hard pressed to find a more divided language than Scheme. As for ISO Prolog, it's not even the most popular standard. It might be in America, in Europe it's definitely Edinburgh Prolog and there's where it's used the most.
You guys are giving me great examples of how interpreted languages without a clear spec + reference implementation completely fail to establish a single standard. It can be argued that in the case of Scheme this is a feature, but for something like Wolfram with an existing closed runtime you definitely don't want this.