@codehunter, it’s just as easy to install a couple of plugins to add CSS and Javascript, and depending upon which one you use, they don’t add a lot of overhead. I’ve seen very, very few themes (maybe less than 5?) that have an option to add scripting code. And some of the themes which include a custom CSS option don’t work very well. There was one theme (I don’t remember the exact one) which used a CSS editor that converted greater than signs (>) into escape characters when the CSS was saved, so you couldn’t use the greater than sign as part of the rule’s selector.
The plugin I like for CSS is Custom CSS Manager, because you can also write CSS that affects the admin dashboard (no theme’s CSS option would do that), and for adding Javascript (including Google Analytics), I like Header and Footer because it gives you a lot of options as far as where you want to place the scripting code (in the header, before the opening body tag, before the closing body tag, etc). So plugins, most of the time, will do a better job than any option added by the theme. Plus, with the way that themes are now required to use the Customizer to set options, the large input fields needed for custom CSS and Javascript don’t fit very well.