Why is Progressive Quaternion Interpolation the default?

Why is Progressive Quaternion Interpolation the default?

I noticed all rotation curves are automatically set this mode at the beginning of all my projects.

I really hate this mode and don't understand why it is the default. The shortest path interpolation creates sharp directional changes at every keyframe and does not create smooth arcs.

Also, when I want to switch to euler angles, I have to do it for every single property one by one? There needs to be a way to switch all rotation to a different mode with one click.

Similarly, when I want to move the timing of keys in the dope sheet, say for the arm, I have to move the keys one by one for every property in the arm. It would be nice to have a filter in the property list to filter only the properties of currently-selected controllers, or by body parts.