Hello,
Question 1 was already answered here somewhere; The materials which are inside the material library are accumulated over time as some of our team members work on them continually. This process was started way back when Physical material was introduced and material library (to some extent) was already present in 3ds Max Corona plugin. It wouldn't make sense to throw away hours upon hours of work which was put into creating these materials. And finally, you can always convert them through our new built-in Legacy to Physical converter (currently per material basis, planning to introduce a batch convert)
As for question two. "Anything over 80" is a general guideline, which can be obviously broken, as it does not cover 100% of the cases. There are instances of 80+ whites in real world. But as always, if a preset makes you think it's unrealistic, feel free to tweak it! In the end, it is your project and those materials' parameters are not locked.
Thanks,
Jan