Why theme is defined at two places ?

in 
nuxt/template/plugins/vuetify.js
and also : 
nuxt/template/assets/style/app.styl

I don't get it. I want a la carte. It seems putting it in nuxt/template/plugins/vuetify.js is useless if already in app.styl . 

But maybe with stuff over my head like webpack styl loader optimizer, you still have to define your theme at both places ?