How will being as stubborn as them make your game experience better?
I understand the consequences of not compromising, but do you really think this community is always going to cooperate? If the community is as good as you think it is, then shouldn't my team always be willing to compromise when I demand a role? Throw in the common mindset that everyone has to carry their team (because their team is weak/unreliable/etc)...if I'm looking out for #1, even when realizing that it's a team game, why would I ever let someone else take "my role"?
Ofc, I don't personally subscribe to that line of thought, but I also won't turn a blind eye to the fact that Riot's refusal to establish at least a default order when communication breaks down is enabling those selfish players in champ select.