I really don't know, but I would guess Google's search engine is almost all C/C++. When you are operating at that scale, it makes sense to invest huge programmer time for very small speed increases.

As to "normal" people, I do a lot of numerical computing using python+C. I end up with probably 90% of the code in python, and 10% inner loops in C. That's typically enough that the C code is taking, say, 50% of the time, at which it isn't worth it (for me) to move more python into C, since I could never buy myself more than a factor of 2 speedup.