You have to change nearly everything about how Drupal works to make it work well on a large site, or a large number of sites. So where is the "standard"? What it does with MySQL DB by default, as one example, is an absolute travesty. Then you run into, oh I can't build my massive site using nodes, it will blow up, so lets use templates, but now we have to mange templates, lets build something for that, oh now caching, how well does it deal with a big server farm, oh need patches and work on that too. Oh it isn't OOP so I have to do alot of extra work and process to keep the maintaince programmers from blowing everything up on multiple sites because they just know a little PHP and want to work in that all of the time vs the system you built.
It is like so many other things, people spend tens of thousands of man hours on making it work, then say, Drupal is great! Just fucking amazes me. Of course Drupal isn't unique in that.