The sex?
If you were 30, single and gorgeous (like Miss Dee), would you want to have sex with overweight, unattractive, married, middle-aged people? Because that's who most 'John's' are. Especially one's with enough money to afford Francine Dee.
And the money?
Most 'escorts' use the money for drugs, gambling and/or shopping addictions or supporting pimp boyfriends/husbands that they swear 'really love me'.
Only a small percentage spend the money wisely.