Crr will never approach 0, it would just add extra white space below the line. The curve is already getting pretty flat on the right side, showing diminishing returns as pressure goes higher.
That's common when charting non-linear data, it makes small differences more distinguishable at the flat end of the curve.
This is common...and very bad form in term of charting data. One should always show the starting point of an axis to show relative scale. Data Science/ Analytics is a big part of my work.
The scale should be uniform linear or logarithmic. Not arbitrary.
Whoever made that chart did that for dramatic effect, nothing more.