A lot of people are eligible for carrier subsidized upgrades every few years as well. When I did this I could have gotten my SE2 for free from verizon from my plan. I chose to pay like $200 premium to get it with the highest storage sku.

It isn't just verizon either. Here is metropcs offering free iphone 13s for new customers:

https://www.metrobyt-mobile.com/cell-phone/apple-iphone-13