To me, it's sort of a discretionary thing. If the airport I'm at is real busy, as in people in the pattern, on the ground and all over, then yeah, I'll probably make a call to let everyone know I'll be taxiing to the active. If it's just me, then I'll probably skip the taxi call and just give a hold short or taking off call as needed. Never a bad idea, but not truly necessary. Do it on a checkride though, the FAA loves that kind of stuff.