Our minds seem to handle only a few orders of magnitude of something, then we need a new name.

For instance, we know what $1,000 is, but instead of 1,000,000 we say 1 million, and 1,000,000,000 is 1 billion.

And we wouldn't say 0.01 million, we would say 10,000 or 10K.

So we don't like fractions smaller than 1, and we can handle 3-4 zeros before switching to a different name.