Phones are one of those systems where they just have to work 100% of the time. Maybe we are spoiled because when MaBell ran things and the government strictly regulated her the performance standards were set VERY high. Most landlines still work even hours into a blackout because of these effects these regulations had on the infrastructure the baby bells deploy.
As a result the IP phone technology is almost guaranteed to require support contracts because when the phones go down business often stops. The only think worse than losing the phones in an office is power failure.