In old Chinese games one sees Black 1 in answer to White's marked stone (possibly White has played tenuki here). These days we call this second-line play the footsweep.
The feeling of Japanese Go under the shoguns was increasingly for honte, i.e. proper moves looking for an ultimate thick overall position. Black in that style simply closes the corner with 1.
Tactically speaking, if Black's footsweep here was answered simply (exchange of marked stones), White has a good play left at 1 (following the proverb 'strike at the waist of the keima').
There is always a trade-off between honte and pace.