What is Bradbury's main purpose in "There Will Come Soft Rains"?

In my opinion, the main purpose of this story is to warn
people of the dangers of relying too much on technology.

In
the society in the story, people have come to rely on technology for everything.  The
house that we hear about takes care of its inhabitants in every possible way.  They
really do not have to do anything anymore.  At the same time, the people have also come
to have too much military technology.  This technology is what ends up destroying the
whole city (and maybe the whole society).

So Bradbury is
saying that people have devised too much technology and have come to rely on it too
much.