Doesn't ML work fine with fixed point numbers? I don't think there is a particular use case for very large or very small numbers.
There's a bunch of work on discretization of models after you've done optimizing them - that works, you can get high-performance inference with low-bit fixed point numbers; but that's after the learning has been done using proper floating point (however, you don't necessarily need high accuracy floating point, e.g. single precision may work betted than double precision simply because it's twice less bytes to copy over).
That's the reason why they introduced https://en.wikipedia.org/wiki/Bfloat16_floating-point_format
It's similar to normal half precision float but the exponent is the same as with 32bit float and mantissa has been sacrificed to get room for it.