I emphatically do not believe that in general, and certainly not of several people who currently are posting in this thread.
If they were to explicitly say otherwise, then of course I would accept that. But I have never gotten the impression that, for several active posters in this thread, would ever consider consulting with their players even for a moment if they believed doing so could even potentially threaten their prewritten setting contents, in any way whatsoever.
Yes, I mean that exactly as strongly as I have said it there. Several people on here have made it exceedingly clear that the setting is vastly more important than anything their players like, want, or take interest in.
		
		
	 
I have said it before but I will say it again.  This would hold true moreso in session 0 or during downtime than during the session.  
I create the campaign first generally.  I do though have friends and when we are sitting around drinking coffee one of them might say "Man I really like X.  Have you ever thought of designing a campaign around X?"   Well if I like X, and probably after it germinates in my mind for a while, I may decide to create a campaign based on X.
How it typically works...
If I do have houserules, and this was far more common in 1e,2e than 3e,4e,  I present them in session 0 along with the general theme of the campaign and how I DM.  This would include the style of game which if I understand trad right it is trad.  Preparation, smart use of skills, effective exploration approaches, and good combat tactics will all matter.  
Now there are flavor restrictions.  I may at any time in the design of a campaign decide to restrict something.  I can say that only these races are available as PC races.  I could say only these classes or only these variations of classes are available.  Most often this is for flavor but there are rare cases where I just hate the race or the class.  I also have a standing rule that only the PHB is assumed official and everything else must be requested.  If I don't own the extra book I will have to buy it.  
Most potential players know the kind of game I run.  If it's a new player that player will usually just go along with what is presented.  All the other players though will likely believe in my DMing philosophy as much as I do.  We may argue about a rule during downtime and sometimes if their arguments are effective I will propose a new houserule.  Many times I won't change anything.  DMing for 30+ years has given me a lot of experience.  Often the new player may at first not buy in totally but in time they often do.  You gain a lot for what you "supposedly" give up.  
There is not the conflict in my games that I think you think there is.  I had a lot of conflict in 9th grade.  Many of my mistakes from those days was allowing stuff into the campaign that didn't fit.  I stopped doing that after a while.  I learned.  So my approach or me and many groups since has worked well and we've had fun.  I think it's a style that could work for many groups.   I don't think it is great for all groups.
I'm not trying to get you to quit playing your way.  I will though defend aspersions cast on my playstyle which is what I'm doing a lot it seems.  And I will admit that when someone is especially snarky I can snark back.  I need to rein that in as much as possible.