Well, there certainly is no shortage of that around here. But, it is truly a sign of immaturity.
I agree, but not in the sense you mean. Age only teaches one to mask it, not resolve it.
There's even a phrase to describe that: false humility. It's just theatre. It is self-seeking and self-serving. In that respect, nearly everyone lacks that maturity.
Genuine humility, that is, seeking and doing good for others with no expectation of anything in return, or more, to one's personal detriment, is exceedingly rare, and impossible to achieve on one's own.
Those who think they possess genuine humility almost without fail do not. And those who appear to BE the most humble are usually the most prideful of all. The genuinely humble are almost always overlooked in this world.
Nice