It is worth comparing the notes of the Blues scale with those of the major scale. Here are the notes of both scales. The numbers written under the note names are the scale degrees which indicate the position of each note in the scale.
Notice that the Blues scale contains both the b5 and the @5. It does not contain the degrees 2 or 6. Altogether, the Blues scale contains six different notes, whereas the major scale contains seven different notes.
The major scale used by itself does not sound very bluesy. However, in Blues, Rock and Jazz, melodies often contain notes from both of these scales as shown in the following 12 Bar Blues.