When you say you paid 0, presumably your just paid for it via a monthly contract over several years?
No. Most carriers have free phone promotions regularly. I paid $0. I think the phone before that was also $0. No impact on my bill (since I was already on the unlimited 5g super speed blah blah blah plan, these promotions serve as a way to get people into the all the bells and whistles $80 plans)
Now, lower cost carriers do less of this, and you need to get the high end plan, so it’s not good advice for everyone to get the free phone deal. It is one way a laptop is different. A decent chunk of people aren’t directly paying for their phone.