Why does it take so long for each generation of wireless communication technology to become broadly available?

Question: Why does it take so long for each generation of wireless communication technology to become broadly available?

Generation of wireless communication technology takes so long to become broadly available devices that enable it are often not available until years after the network has been fully rolled out. Current wireless phones include 3G and 4G networks, Bluetooth device and wifi technologies. Wireless communication technology transmits information over the air using electromagnetic waves like IR, RF ,satellite etc.