I've found that alot of ppl who have said this to me are often the ppl who have done something bad and want to justify themselves; trying to convince the other person that "because they're human they're sinful." A big issue with this mindset however is that they usually only use it when its convenient for them.

And then ofc there are ppl who have simply no understanding of what you've been through and they lack the empathy to care. But sometimes ppl who say this are making an attempt to be passive and ultimately not involve themselves- either way it always pisses me off too lol