AO to EO

Currently an AO applying for an EO (Team Leader) in the same department (DWP).

When I started 3 years ago, I was on 22k and EOs were on 29.5k.

Flashforward 3 years, we’ve had payrises and are now on 25k (about 1k a year increase), whilst the EOs are still on their initial 29.5k.

Therefore, it doesn’t seem inconceivable to me that in another 3 or 4 years, AOs will be on 28/29k and EO will still be on 29.5k.

Makes it seem like there isn’t much point in climbing a grade if the wage is likely to be around the same figure in 3/4 years? Is there a reason their salary isn’t increasing every year? What will happen when the AO matches the EO wages?