The "everything turned on by default" concept is part of why Windows is bloated and insecure.
This is changing, but part of what I like about Linux is that it makes less assumptions about what you are doing and assumes a (at least somewhat) skilled operator. Part of what I dislike about Ubuntu is that it makes too many assumptions about what I want to do. It's also why multiple Linux distros that target different audiences are a good thing.
The points here are that :
1. All optimizations or assumptions make something better for a certain task or use scenario.
2. Any optimization that makes something better for a certain task or scenario will be worse for a different task/use scenario.
Think of strong versus lightweight -- it's a tradeoff.