When I first started working in studios the difference between mono and stereo was much clearer. Part of the reason was track count, sometimes you only had 24 to 48 tracks for all your music and vocals. So if a kick drum was only one channel you wanted to make sure that’s all it took up. Now with everything in the box, everything is “stereo”. All the software instruments are stereo so they all end up getting tracked out that way. The issue is a lot of the instruments are only mono tracks but look as though they are stereo. If you take a single vocal track, duplicate it, and pan it hard left and right it’s still mono but 3 db louder.
In the video below I go over the difference between mono and stereo tracks and how to tell the difference between the two. If you have any questions hit me up at my mixing and mastering site here.