Hussar
Legend
@Hussar, I think the background idea has some merit.
At session 0 most of what comes up is - selecting a setting, cosmology, level of magic, the difficulty, playable races/classes, published material allowed, house rules, genre...etc. What hardly or never comes up (at least at my table) is what each player perhaps likes least. It would be a good way for the DM to gauge what would be most enjoyable at the table by backgrounding some of these story components
Whether I'd agree to background something as pivotal as a Warlock's patron would largely depend primarily on my knowledge of the player and his/her maturity level, length of the campaign and the overall campaign story.
Oh, yes, absolutely agree with this.
I probably wouldn't background stuff later on. Maybe I suppose. For example, the monk in my current Thule campaign has a bar. It's not meant as a major plot thing, just somewhere to hang his hat. It wouldn't bother me in the slightest if he said he wanted to Background the bar. I have no real plans for it, so, AFAIC, I give up nothing doing so. So far, it's just been a bit of a background place anyway.