Why?

Just as a question, why do people freak out or shut down when they play? I'm still a newbie but I was trying out a mech build from a recent daily in unranked and noticed my opponent saw the mass hellions and continued to get mass lings. My opponent was a fellow noob that time but in another instance my opponent was silver. He saw I forgot to get air support and would be raped by banshees but kept trying to get more tanks than me; even though my tank count was clearly well ahead. I was just wondering why people either freak out when they scout or just completely ignore their scouting information like they never scouted. It just seems bizarre how much I see it.