I found that sometimes you use multiple stylesheets. However I don’t understand why you need to add many different files even though they are all css file. Isn’t it makes it more hard to control the code and lower the readability? Then, why is it necessary to use multiple css file?
A lot of it is often personal preference. When you have a large number of different styles sometimes you’ll want to split it up, maybe into sections (article styles, nav bar styles etc) or maybe for readability. Some people prefer to have one large file that covers everything and find that easier, it’s mostly preference! For most coding I personally like having many short files over one long file.