You may think its not required, but when you get turned over by a client or an insurance company you will wish you had it.
Furthermore, failing to advise an insurance company doesnt mean they wont take it into account. I would be pretty certain if the insurance assessor turns out after a break in and see's the alarm panel theyre gonna ask the question was it set? If it wasnt they wont pay out, if it was they'll come looking for you!