I must respectfully disagree. Having sailed extensively offshore on a Hinckley yawl, the Mizzen mast allows you to to place many accesories on without having to put all that stuff on the main mast, wind generator/radar/AIS/VHF/Sat phone etc. When the wind pipes up you can sail jib and jigger and not have to worry about going on deck to reef the main. At anchor you can raise the Mizzen sail and use it as an anchor sail. Not to mention how pretty they look!
Beware though I have a contract on a Crealock 37 yawl so I am probably not thinking straight.