Let me give you an analogy. Your question is equivalent to asking the chef: the recipe says that Sichuan cuisine has fried beef with bitter gourd, while Cantonese cuisine has fried beef with bitter gourd. Master, why do you think there are bitter gourd fried beef everywhere?
Friend, I'll give you a suggestion: for beginners, it's best to play more songs according to the guitar score first, and don't do too much research on the theory (it's easy to be self-defeating, just like your question). Quantitative change will bring qualitative change. If you play more (for example, you can play thirty or forty songs), you will naturally understand a lot of things (because these songs will definitely contain big and small sounds and various modes).
At this time, if you look back at your question, you will feel very strange. .....