Mila-disappointment from Mildays

My son wanted to open an account for me at Miladys recently. Because plus size clothing is very sc**** he thought it would be a good idea. When wr arrived at store to apply with his credit score of 630, he was declined to our surprise. The store undertook to investigate the matter and revert, but has since not bothered to call us. I am disappointed in Miladys as they could have called us back but also because they declined him from credit. He had a Truworths account which he managed perfectly. He never exceeded his spend, kept the credit on the account after first buy, settled the account in a shorter period and closed it since. Why would stores do that?