And when you will leave your enterprise, your code won't be maintainable anymore because the next developers will have no idea about the architecture of your application. Then someday someone will say "well ... nobody understand this code anymore ... let's get ride it, guys. I guess it's time for feature freeze.".

Of course, we're talking about some size of application here. If you just want to make a todo list, jQuery is fine. But when dealing with a potentially huge codebase, it is good to enforce practices.