Question about the way you use customize

[dabrahams]

Hi there; I'm exploring your dotfiles for inspiration as I go through my umpteenth everything-bankruptcy. I didn't know a better way to ask a question, so filed an issue. I notice you don't use custom-set-variables anywhere, for reasons I think I understand, but you also make extensive use of defcustom and defgroup. Would you mind taking a moment to explain your motivation and approach?

Thanks in advance!