Nobody stated Hosted VOIP. Just Voip.
A point that was being made was that there may be others issues to overcome in this system if you point them out. Utilizing low cost SIP trunks could be a benefit to some customers.
Advanced features in newer voicemail systems that are not supported by an old MICS system is another reason. Heck, video features could be another, there are many.
It is equally as senseless to believe that the only solution is to provide a reel of copper between the building and the guardshack to provision a digital line from the MICS.
And, there is nothing wrong with throwing out old phones, if they don't meet todays needs. And, older phones typically cost more to maintain, and lack some of the newere features that some newer VOIP phones can provide.
What was being suggested was to look at the entire network and ensure you weren't missing other sales opportunities, and feature benefits by proposing a new solution.
It's one of many options, and a valid option that some may disagree with.