Buttonhole forms tend to be used for decorative needlework, such as the edges left in cutwork, while blanket stitch forms tend to be more practical (literally neatening the raw edges of a woollen cloth used for a blanket).
Source: THOMAS, Mary (1934). Mary Thomas’s Dictionary of Embroidery Stitches, London: Hodder and Stoughton, pp. 17-18.
GVE