Yahoo bought Viaweb from Paul Graham and rewrote the Lisp application in C++ and Perl. Reports are the results were strictly inferior but it achieved the goal of not having to rely on Lisp programmers.

Part of Yahoo's business is/was hiring programmers reasonably cheaply and controlling them reasonably easily - to allow Yahoo itself to sell parts or all of itself.

So things aren't quite a simple as "this doesn't serve the product", sometimes the engineers (and their replaceability) are part of the product.