Many people confuse being self-effacing with politeness.
When complimented, instead of saying a simple thank you, they disparage the compliment. I don't know why I put it on. This is possibly because they have been taught that accepting compliments is somehow akin to having a sinful pride. I'm not saying anything is wrong with their teaching. I'm just wondering if maybe they've grown past their upbringing and are ready to rethink where their lives are headed.