Because the simplest rhythm is 4\2 beats, which is strong, weak, strong, weak. Then it may develop into 4\3 beats, strong, weak, weak, strong, weak, weak. There are also 4\4 beats, strong, weak, sub-strong, weak, strong, weak, sub-strong, weak. There are more music in 4\4 beat, so the most basic notes are usually quarter notes in the process of musical expression. In order to express more coherent music, the quarter note will be split into two halves, resulting in the eighth note, and then the sixteenth note will appear. The advantage of dismantling it this way is that it can retain the original rhythm without causing confusion.

Occasionally there will be other splitting methods, so use 3-tuplets, 5-tuplets, etc.

Please adopt if you are satisfied