Why wouldn't one use some sort of pseudorandom seed instead of just uninitialized memory? Couldn't one sample a clock, image sensor, thermometer or some other

Why wouldn't one use some sort of pseudorandom seed instead of just uninitialized memory? Couldn't one sample a clock, image sensor, thermometer or some other sensor that would have a random value to use as a seed? Seems like a part of memory allocated by the compiler might always be zero.