What are advantageous features are in SCSS/Less/Sass vs <?php header("Content-type: text/css");

I’m a long-time PHP developer, and although I’ve done lots of clever things with CSS, I’ve never really gotten deep into SCSS/Less/Sass.

Working in LAMP stack, I’ve never seen anything from SCSS/Less/Sass that I couldn’t do better by just having my “css file” be a .php file with

<?php
header("Content-type: text/css");
/* Variables to be used in the following CSS heredoc */
echo <<< CSS
/* Lots of CSS code here that grabs calculated variables when I need them */
CSS;
?>

In a LAMP stack, this strikes me as significantly more versatile and straightforward than installing additional SCSS/Less/Sass compilers and following their syntax, and it allows the full language to come into play.

Yet, I see SCSS/Less/Sass used all the time in LAMP stacks, and the header technique I almost never see used except by myself and a rare few others. I’ve tried both SCSS/Less/Sass a few times, and just got annoyed by the limitations. What am I missing?

What are the features provided by SCSS/Less/Sass that are missing by just creating a PHP filed with a css header declaration?

(The only one I’ve found on my own is that old versions of IE will insist on treating the .php extension as -not- a css file, but that’s easily addressed by a one-or-two line .htaccess redirect,

but that minor one-time inconvenience doesn’t seem to balance out the loss of functionality?).

What are advantageous features are in SCSS/Less/Sass vs <?php header("Content-type: text/css");