Because why not? CSS is not like C code, speed or efficiency is really not that important here, reliability is. If it works you can use it or not. We're talking

Because why not? CSS is not like C code, speed or efficiency is really not that important here, reliability is. If it works you can use it or not. We're talking about shaving a few K at most off your file as the main benefit or maybe some minor compatibility improvements. These are important in some cases and unimportant in others. CSS solutions often are not one size fits all. Also it's important to know how these things work and I would posit it's probably easier to write one than to decipher someone else's code that may or may not have had the same goals as you. Beginners are going to use whatever they always use, which is the thing that comes default or is the most popular. It's also a nice way to pad your Github for job apps.