People are going to judge you based on what they see – give them a little help with a convenient, at-a-glance summary of others' opinions of you. And if your score is low, hey – your refreshing candour is probably good for another half star.
Well, maybe you're so-bad-it's-good bad as opposed to plain old so-bad-it's-appalling bad.
You're too modest to make an exhibition of yourself with some vulgar, flashy display of competence.
You're the conservative choice. The safe pair of hands. Competent – but not too competent.
You're actually a four – or you would be if it wasn't for your irritating false modesty.