So yours updated about every 8-9 days compared to my (way shorter timeline experimental average of) ~40 days. I'm guessing ISPs officially want to err on the side of expecting your IP to change more often than not. Probably for CYA reasons
I do not understand why they don't sell static IP addresses, either. They did that back in the DSL days. Also, why no IPv6? It's just weird.
Similarly, Comcast does IPv6 to its residential customers, and even tiny VersoNetworks in Denver can manage both IPv4 and IPv6 to its customers.