Why values within a "Style Box" are discrete and not continuous?

Question

Style Boxes map financial products on a two axes diagram, but instead of using continuous values for the axes, they use discrete values (small/medium/large, value/blend/growth, etc.).

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How is this useful? Why should $1 be able to shift a product between squares? What's wrong with using for example the actual (normalized?) market cap on one axis and the actual (normalized?) P/E ratio on the other axis, in the familiar Cartesian representation?

Answer 1

It appears that in 2016 Morningstar presented a new framework for style box based analysis, which is continuous:

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Another document from 2004 shows a similar continuous nature:

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