Resistance and stubbornness from the old guard isn't slowing things down.
Just because a new fact or idea seems right, doesn't mean it will spread like wildfire. Evolution, hand washing in hospitals, the inevitability that personal computers were the future of technology — none of these ideas were accepted immediately, even though they seem obvious today. Change takes time. But why?
The short answer is we're intellectually stubborn. We don't always weigh all the evidence before we make a decision, and this is especially true if a change of opinion requires a wholesale overhaul of our worldview. Usually, we're defensive in the face of change, spouting alternative theories and contradictory data. Although this type of resistance can help keep everyone honest, it can also produce very bad effects.
Just take Ignaz Semmelweis — a physician who recommended doctors clean their hands prior to delivering babies — who was ignored and essentially driven mad by his colleagues' refusal to accept the truth. But eventually, in the face of overwhelming evidence, the majority will generally accept the new theory, before their recalcitrance becomes too counterproductive.