why some black holes rotate?

Those black holes which rotates on it's ow axis are called a rotating black holes.find more definition of black holes here.

so why some black holes rotate and some not?

we all know the Newton's first law of motion:

A body continues it's state either rest or motion until a external force is applied.
Same with black holes more often black holes are formed due to died star or when somehow star collapses in it's core.find more how a black hole is formed here.

Star keep on rotating even if is a black hole now. And becomes a rotating black hole.

why some black holes do not rotate

Their may be star in the universe which do not rotate but in my thought non rotating black holes are very old black holes which rotating slowly stopped due to friction.

But still their is no scientific prove how non rotating black holes form.

as black holes get old do they die?for the answer click here.