Generally, insurance patients are more easily referred and generally don't pay much more than what they are expecting to pay based on their insurance (they'll pay a copay or whatever else they need to meet their deductible). They have much less effective income to lose in seeing you, so they are more likely to keep going and feel they are losing money.
Cash patients often already have insurance and are choosing to pay a premium to see you outside of their insurance system, and are more likely to pick you based on your perceived quality or lack of waiting times. Cash patients can always decide to fall back onto insurance or take their business elsewhere if they don't feel you are worth it, so retention in understandably lower than with insurance patients. Cash patients are also more likely to stop going to appointments to save money than an insurance patient. Et cetera...