In our field, tools get chosen not by merit but by what's the current fad. It's unfortunate, but this fact makes those two questions unhelpful in moving the discussion forward.
That's an idealistic and elitist response.
Very removed from the empirical and scientific spirit, which would suggest that if people use other languages for large projects (say C/C++) there are reasons for this, besides them being "fashion victims" and "doing it wrong".
Some of those reasons would be the appropriateness of those languages for the computers of the 70's - 90's (at a time when Lisp machines were slow and resource hungry), or the availability of tons of library code afterwards, the better control over the memory layout needed for large scale projects like a broswser, an OS, Office or Photoshop, etc etc.
Notice how the response just moves the goalposts a little further, without trully answering. Even, for example, if you are right and languages are used because they are fads, you failed to answer why LISP wasn't picked as a fad itself.
But there are mechanisms which may look like 'fad'. For example in the academic community a lot of progress is only incremental and people need something new to publish incremental results.
Industry demands from Universities to teach the language de jour.
'Industry analysts' give technology guidance and tell companies what to use.
Often it is seems 'modern to reinvent everything. Look at Clojure, a Lisp dialect which is basically zero backwards compatible. It allows people to reimplement the old stuff, sometimes in slightly different ways and claim some achievement. You also don't have to deal with the old people, which 'know it already' or with 'old' technology. The community is self-selected to newcomers and those willing to reimplement old stuff and to invent newish stuff.
It is also about communicating ideas. If one uses a language few speak, one gets less attention, mindshare, etc. Thus use something which in the hype cycle is on an increasing angle, where the attention of many is easier to get. If one wants to promote a new framework, better use a popular language underneath it. Otherwise it could be nicely engineered, but few will hear of it, few will try it and few people will use it.
Also some technologies are popular - like the JVM - and this allows to leverage engineering efforts by others. Popular technologies often seem to be ported widely and seem to have more active maintenance.
Tooling, Library, Schooling, existing base of people that know the language, CPU architecture, Memory constraints and so on. And of course all the nontechnical things like marketing.
So saying that there is not as much lisp as c++ code is not a argument that c++ is a better language.
Might be possible for a totally academic or greenfield small time project, but not at all if you do commercial and pragmatic oriented development, with teams, constraints, deliverables etc.
So while I agree that "that there is not as much lisp as c++ code" is not a argument that c++ is a better (core) language, I also think that this fact shows that C++ is a better language+extras for more projects.
