Why does the CDL manual specifically call out on-ramp and off-ramp curves as a rollover concern for tank vehicle drivers?

AAMVA CDL Manual, Section 8.2.1 (High Center of Gravity), p.8-8-1

Ramps are frequently the site of real-world tanker rollovers because their curvature can be sharper than drivers expect. Recognizing that the same rollover physics apply there as on any highway curve reinforces consistent, cautious speed habits everywhere a tanker turns.