This new intern chose to write CSS instead of LESS/SASS even though I showed him how much time/lines of code were saved using LESS because he was "so used to it". Go ahead.. Enjoy writing 1 million lines of css to accomplish the same task.

Don't get me wrong, CSS preprocessors can save time and help organization, but it really depends on the project it's being applied to and how that project uses elements on a page. I personally never use LESS/CSS/Stylus/[whatever other preprocessor] because it creates a few problems.

1.) I now need to rely on something to process the pre-processed CSS into a production-ready stylesheet before it is production ready. If I rely on a javascript-based processor, that's more unnecessary overhead on the page. If I'm on a different computer, I need to install that preprocessor's or find a web one.

2.) If there is a minor emergency and something needs to be fixed on the CSS while I'm on the go, I have one of two options. Either I open the production, minified CSS and make my edit, or I need to install said processor, edit the preprocessed code, process it back into production ready CSS and upload it. Neither option is fun when I'm needing to modify this while all I have on me is a phone.

3.) In the past 10 years of front-end development, I have NEVER needed a CSS preprocessor. Why? Because I have never needed to write more than 2,000 lines of CSS at the very most. Typically I have an entire website designed writing at most 500 lines of CSS for the design and another 150-200 for the responsive adjustments. A preprocessor's methodology of organizing and ordering code actually hinders my ability of styling a website fast and putting it in what I feel is a more human-friendly structure. Variables and mix-ins are nice and all, but not at the cost of what I feel is an unnatural order of operation and less freedom of specificity.

All of the above is subjective of course, but for me a CSS preprocessor does more harm than good on my own productivity.