Because of how floating-point numbers are distributed, you should expect a random number drawn uniformly from [0,1] to basically never hit the smallest floating-point number: hitting something in the range [0, 2^-n] should happen with probability 2^-n.

I agree there is much more one could want out of a uniform random float generator than just k/N where k is a integer drawn uniformly from {0, 1, …, N}, but hitting arbitrarily small floating point numbers is not on this list.

If you are intending to sample numbers in the range [0,1] such that each float occurs with equal probability then that’s fine, but it’s certainly not uniformly random on [0,1].