I have to wonder, why can't their wi-fi be disabled? Is it one of those scenarios where it is being used to support other ISP customers in your area?

My ISP (note: also owned by my employer) doesn't have this, so the modem I've got is theirs, but I can disable wi-fi. I do, too, so the only client on this thing is my firewall. I assume that everything past my firewall could potentially be hostile.