I hear this over and over but I don’t think it’s universally true.
For me, when I was still a believer, I thought and said (at one point) that religion was needed for morality only because I didn’t think too hard (as is true for many religious folk) and also because if people could be decent and moral without religion it called into question some fundamental tenets of Christianity.
At some point not long after I said this to someone, who called me out on it, I realized this idea was stupid and was easily disproven by the many good, non-religious people I knew. That was one of many realizations on my path to deconversion.
Another was encountering religious people who seemed not to have any empathy (or who had been brainwashed into having none). So probably some make that claim who are sociopaths. Anyway I was horrified by some of the statements and attitudes and that prompted further thinking.