It’s a question of context.
Your educational certificates are of less significance when you have 15,000 hours and 20 years experience of flying. However as an apprentice or somebody starting out in a career, you are going to have very little attainment to offer beyond your educational achievement. As always it’s a case of competition. When you are making those applications you are going to be up against hundreds of other applicants and only a small percentage of those applications are going to advance to the interview stage. It is better to be able to show grades that put you in serious contention with the competition. This is particularly so when that competition is fierce!