I need results from market or academic research that can tell me why
people sign up for home Internet service.

I need to sort out the following:

a) Do people generally sign up because they want to use email? Because
they anticipate searching for information? Because they want to shop
online? Because they want to see what the Internet is
about but have no particular activity in mind?

b) Aside from being willing to pay, do people who sign up to get
Internet service at home "value" by some measures the Internet more
than people who go to a library, school, or some public place to use
it?

I'd be happy to provide more information.

silkstocking-ga

Are you referring to any particular point in time?  Do you mean for
all people who now have Internet service or those who are currently
acquiring service for the first time?

It might be easier to answer a series of questions like:
What percentage of people felt email was part of their reasoning
  for getting service?
What percentage were motivated by online shopping?
What percentage had no reason?
... and so forth.

Most people need multiple reasons to pay top dollar for a computer
plus a monthly service fee, so assigning a single reason to each
consumer may not be practical.  Also, a series of questions may allow
parts of your overall research to be completed even if the rest
cannot.