Also it helps for memorisation because it lets you actually understand the patterns and what they mean. Otherwise many people just blindly copy the notes.
Besides, we must not forget that harmony is a preparation for improvisation and/or composition. Every organ composer or improviser we know was first a master of harmony.
In early days, they might call it (and teach) differently - thoroughbass, basso continuo or figured bass. But all these terms refer to similar things - rules of voice leading, chord relations, and functional harmony.
I am aware of the need of a beginner level course in this field designed specifically for organists, with assignments both on paper and on the organ. However, I'm not sure if enough people would raise their hands to participate.
I'm thinking about an introductory Harmony for Organists Level 1 course which would last 12 weeks and incorporate exercises presented in PDF format and with my audio explanations and examples played on my organ.
If enough people would say "Yes", I could begin the necessary preparations and we would be ready to start in a few days, I think. So if you would be interested please let me know.
To your success,