You make a good point. One thing we need to remember is "religion" mainly means practiced rites, rituals, and habits that people hone with a certain purpose or goal in mind. It doesn't NECESSARILY mean any belief in something spiritual. It just happens to be that spiritual beliefs yield religion in people.

Like when Jesus was around, he was stomping on people's religion, trying to show them the truth they were all missing. That's why he was crucified, he argued too well against their established religion and threatened the good thing they had going. He wanted them to see it's not about what you do, but Who you trust in.