I personally believe that Verizon is doing this to "force" us to use their own Visual Voice Mail system. 

Right below the "Set Password" button is a "Visual Voice Mail" button.  If you push that it will step you though setting up Verizon's $4.95 plan.  They want to make getting your voicemail the old way (or via another vendor like YouMail) difficult and/or impossible to make more money.