I’m more of an insect and rodent guy, but I’ll take a stab at it.
Actually, woodpeckers, from what I know of them, actually do peck wood “for the heck of it.” Or what passes for that to our minds.
Keep in mind, humans apply human logic to what they observe. Animals work on instinct, and a woodpecker’s instinct is to peck holes in wood surfaces. While this often provides food for them, they also do it because that’s how they create hollows for their homes, and they do it because…well, it’s what they do.
That being said, there may actually be insects in the house (although if your parents live in the northeast, you know how cold it’s been, and there would be evidence of infestation inside the room where the birds are). An inspection by a trained pest guy may be in order, but I doubt they have a serious insect problem.
As far as repelling the birds, I’ve heard owls, rubber snakes, etc., work in the short term, but Q.E.D. is right: once they become accepted as part of the environment, the birds ignore them.
Your parents may do better if they install some kind of whirlygig around the area. Constant movement will spook the birds. It may work better if they’re shiny, too, and catch the light. Flashing lights are not real popular with birds.
Now…why is this happening now, after 30 years of homeownership? Simple. Expanding territority. Your parents’ house happens to be within the range of this particular bird.