The, code is much more readable then the same written with inline styles.
Citing their website:
Most approaches to styling inside components rely on inline styles, which are limiting. Atomic CSS, like inline styles, offers single-purpose units of style, but applied via classes. This allows for the use of handy things such as media queries, contextual styling and pseudo-classes. The lower specificity of classes also allows for easier overrides. And the short, predictable classnames are highly reusable and compress well.
Citing their website:
Most approaches to styling inside components rely on inline styles, which are limiting. Atomic CSS, like inline styles, offers single-purpose units of style, but applied via classes. This allows for the use of handy things such as media queries, contextual styling and pseudo-classes. The lower specificity of classes also allows for easier overrides. And the short, predictable classnames are highly reusable and compress well.