Does anyone know why the 48 volt battery has been removed from telephone?
A wired line operates on 48 to 52 volts DC. A cordless phone's base unit is designed to work With that, but not From it. The base uses AC power to charge the battery in the handset and to transmit and receive signals between it and the handset. That's why cordless phones don't work during a power outage, but regular phones do. There is a lot more going on with cordless phones than you seem to imagine. You might do yourself a lot of good by learning more about technology in general.
Per: "The long range one with the smart computer has a battery." Internal base batteries run the radios and display functions. The 48 volt line is virtually (except in rare antique configurations) only there for signalling continuity. It is like a keep alive signal and a demand for service signal. It was used, in addition to that, to provide talk battery that got modulated with voice. But your "Long Range equipment transmits an internally powered voice signal using a replaceable or rechargeable battery set now days.
Phones that attach to the phones land lines already HAVE 48 volts, from them, over that same wire.