It allows you to instantly transpose songs between scales and keys.
I like to sequence songs using harmonic mixing, i.e. putting songs in like scales back to back, and by composing in C Major you create a work environment where any song Can at any time be transposed to any scale without destroying its structure as a song in terms of intervals and chord progressions etc
It is also very helpful for music theory because you can at a glance see what chords (I IV V VI) and intervals you are using in any song no matter what the scale is.
Transposition to a new scale doesn’t work with regular scale locks unless you rewrite your song totally.
Sometimes I even export 4 or 5 variations of a song in different keys & scales to pick one.
It’s doable with the vsts Cales Scaler or Komplete Kontrol but some DAWs it’s built in.
Additionally, this makes it much much easier to type in scale notes on a computer keyboard. Z X C V is always 1 2 3 4 in any scale, with the current scale lock you basically need to figure out which random keys on your computer keyboard correspond to the root note etc.
It also adds functionality to devices that don’t have a lot of buttons, for example I have a controller configured to play only the c major notes in every octave and this way I can use those seven buttons for every single one of my songs without having to worry about the fact that I don’t have a full 12 note chromatic keyboard in front of me.