Question

Why society might initially reject a new scientific theory?

Answer 1

I was about to say:  because people generally get comfortable with
what they think they know, and don't like the discomfort of being told
that they have to change something they're comfortable with.

But then I thought about it a little bit more, and I have a different answer.

"Society" might initially reject a new scientific theory, because 'society'
is totally unequipped to render judgement of any kind regarding any
development in Science. 

First of all, 'Society' is a thing that's made of a bunch of people, so it's
inherently unequipped to deal with scientific news.  Anything that 'Society'
decides has a lot of the mob psychology in it, and a public opinion poll or
a popularity contest are terrible ways to evaluate a scientific discovery.

Second, let's face it.  The main ingredient that comprises 'Society' ... people ...
are generally uneducated, unknowledgeable, unqualified, and clueless in the
substance, the history, and the methods of scientific inquiry and reporting.

There may be very good reasons that some particular a new scientific theory
should be rejected, or at least seriously questioned.  But believe me, 'Society'
doesn't have them.

That's pretty much why.