It will also protect a lot of consumers that do not understand the difference between clearing history and clearing cookies/logins/etc.
I suspect that this is part of Apple's push to be seen as more secure and privacy-friendly than the competition. Defaulting to clearing everything can help prevent unauthorized access.
Right, wrong, or indifferent, they'd probably tell you to use a Private Window for the things that you don't want stored in your history.
How about giving people a choice? That would make them wonder what the differences are and educate themselves rather than being forced a certain method that will likely confuse them further. Sometimes when you decide for people, they resist and will most likely be confused. In this instance, having to re-authorize your computer(s) every time you enter a bank/financial site or having to login to your accounts when you're not used to it makes it more cumbersome, not secure.
As for private browsing, many like to revisit sites in their history (which they clear once done for the day) and it won't save authorized logins. So that isn't an option, I've tried.
Keep in mind, we're tech savvy, the majority of computer users are not.
btw, I found many are not clearing their history as they don't want to go through all of it over and over again, and don't know how to clear just their history, which actually makes them more prone to security issues.