It's also a "how much exposure do people have if the private key is compromised?" Yes, its to make it so that a dedicated effort to break the key has it rotate

It's also a "how much exposure do people have if the private key is compromised?" Yes, its to make it so that a dedicated effort to break the key has it rotated before someone can impersonate it... its also a question of how big is the historical data window that an attacker has i̶f̶ when someone cracks the key?