You’re being nieve when you say that. What do you think you do when your mix sounds right? You’re mixing using maths, because that’s how music is created, if you choose to ignore it that’s up to you, but I want to have all the tools I can to make my set sound good every time. Do you think any big DJ plays by ear when they go play at a club or festival? Or they prepare a set in advance at home, set cues, practice, practice and practice? I used to write notes on my vinyls to make my life easier, this is the same but gone digital. If you can do a set with no cues, or visual aids whatsoever kudos to you, I could but I rather not because I have a day job.