Blind Pick is so annoying >.<

Why can't people realise they won't always get the roles they want, and adapt to new ones?

For instance, I just joined a game where i called adc first, and someone else called adc after me. I waited a bit to make sure they werent gonna adc, and if they were I was to change my role for the sake of the team. But they didn't say anything so I let them know im going adc and I locked in. After I locked in, he flamed and locked in ashe. anyways, no biggie cuz i dodged but it's so annoying ugh t.t