I would assume the answer was speed. I was also writing some spaghetti PHP code around 2007 and remember making choices that were the benefit of reducing serve

I would assume the answer was speed. I was also writing some spaghetti PHP code around 2007 and remember making choices that were the benefit of reducing server stress while making my life harder. No framework was a big one. Remember, Friendster died due to crashing and Facebook, for all its spaghetti code at the time, was remarkably solid and rarely crashed. It is easy to forget how hard the sysadmin side was for a growing startups before we could spin up infinite cloud servers and VC wasn't just an open spigot for anything with growth. Remember the fail whale on Twitter?