Probably he is saying that because their expertise and focus lies in backend, it's costlier for Google to increase frontend service and server compared with say, other web-hosting companies.
People who are downvoting me don't really understand what I'm saying. I'm finishing up my internship at Google now. This is a nomenclature problem -- what ChuckMcM is properly referring to is front-facing backend vs "back" facing backend. They're really just two different types of backend servers. SREs manage both and they are installed similarly. It could be argued that Google perhaps has certain weaknesses in frontend (i.e., UI/UX design), but this is clearly a case where engineering talent is not lacking -- they're the same engineers as the ones working on private servers.
