Disappointed outcome

I app**** for an overdraft and I was told that I have qualified I just need to send documents that they need to verify. After some few days after sending the documents then I was sending an email declining my application and the the reason being I will go take out credit from other institutions. I found that reason very strange. I have been banking with the bank for over 3 years without any default and I am getting bonuses every months that are deposited in the same account on a different pay dates.

My question is why other bans which are their competitor want to offer me better benefits than my bank that puzzle me. Maybe is because I am not white enough as my credit score is good. This is my last month using this bank