[foobarrio]

You're missing anything that uses notes outside of a typical diatonic scale. Example: The first 2 notes of the popular piano piece Fur Elise. It uses an Eb. The piece is in A-minor/C-major and Eb isn't in that scale. That piece also uses a G#. The addition of the Eb and G# means you need at least 9 tones to represent that melody.

Many Spanish songs use what's called the Andalusian Cadence which will use the equivalent of that G# in melodies too as well as the non-sharped note.

Any blues singing will use that "blue" note that is off the diatonic scale.

A song like Jamiroquai's Picture of My Life has a little color note that feature prominantly in the melody in the opening line "... I can follow through." The note on "through".

[dragontamer]

Blues has more than one accidental: https://www.basicmusictheory.com/img/c-blues-scale-on-treble...

Blues scale is also 7-notes instead of 8.

[foobarrio]

I play lots of blues guitar, I am familiar. That chart is basing it off the C minor scale which would correspond to the Eb major diatonic scale.

If you play an Am blues scale which is, you'll see how the blue note is really just one note (it's a pentatonic scale with note between the 4th and 5th added): it would be A C D (D#/Eb) E G A. That D# is the blue note.