A Scale is a collection of pitches that work together in order to achieve some melodic-harmonic purpose…
There are many kinds of melodic-harmonic purposes; there are many kinds of scales.
Each scale type has a unique personality. Each scale type sounds different. More important, each scale type feels different.
Each note in a scale has a particular musical function. Some notes establish the tonality. Some notes create melodic-harmonic tension. Some provide melodic-harmonic release.
Think of each scale as a distinctive palette of musical sound-colors that work together to create a certain mood or feeling. Never think of a scale as an unbendable or unbreakable rule.