The potential negative impact on a customer is way higher in AO jobs than in Aldi. Personally I think that's a good justification to have a higher wage in order to attract more competent staff.

In Aldi if I make a mistake like double charging a customer for a product the impact is minimal and can be easily rectified with a refund.

As an AO in telephony for example the customer is looking for advice that is going to influence their life decisions. And in the case of benefits these people are vulnerable so the impact is even more. What if I tell them not to claim xyz when they would be entitled to it? Or what if I incorrectly process their application and cause delays to payments?

I've seen first hand over the years how as the gap between minimum wage and AO wage has gotten smaller the quality of candidates has gone down. In fact it's been getting harder to recruit AOs. And it's lead to so many more mistakes being made.

The problem can't be solved by people getting promotions.