Programming a globally unique ID per device is a large added cost for <$0.01 devices. The device needs fuses or equivalent so it can 'remember' it's 64 bit ID. it needs logic to both program as well as read the fuses.
Think of applications like LED controllers - previously with I2C all they needed was an 8 bit shift register + comparator for their address, and an 8 bit shift register for their 'brightness', and an 8 bit comparator and +-50% RC oscilator for their actual operation. Probably ~400 transistors.
With onewire, they need a 64 bit address shift register, an oscilator, a state machine for bus states, a counter to act as a timer for long/short bits, multiple comparators on the timer output. I don't think you could do it in less than 1000 transistors. Doesn't sound like much, but when every LED in a million pixel LED wall needs one of these circuits, it adds up!
Think of applications like LED controllers - previously with I2C all they needed was an 8 bit shift register + comparator for their address, and an 8 bit shift register for their 'brightness', and an 8 bit comparator and +-50% RC oscilator for their actual operation. Probably ~400 transistors.
With onewire, they need a 64 bit address shift register, an oscilator, a state machine for bus states, a counter to act as a timer for long/short bits, multiple comparators on the timer output. I don't think you could do it in less than 1000 transistors. Doesn't sound like much, but when every LED in a million pixel LED wall needs one of these circuits, it adds up!