Because - speaking from a lot of experience, both personally and professionally - human beings hate bad news. They reject the wet blankets, the naysayers, the doomers, the party poopers...you get the idea. I mean, the fact we have so many metaphors for the act of being the person giving a group bad news, should tell you how poorly humans look on it. Humans want to believe the sun will rise tomorrow, the birds will sing, the lines will go up, and everything will be fine (or better) than it was yesterday.

This attitude is especially prominent in tech. There's a very real desire to immediately replace whatever was old with whatever is new, regardless of utility or viability. We're participants in (or supporters of) a system of startup-expansion-acquisition-repeat that only focuses on building something new that has a perceived valuation, not something that's actually beneficial. There's no attitude to look back or be objective, because tomorrow will just be better anyway. So when your business leaders, capital investors, regulators, engineers, and developers are all "high on their own supply" of new > old and complex > simple, that attitude seeps out into other aspects of society as a whole.

Nobody likes naysayers who are right. It's just our curse, I guess.