Did you hear the one about the 40-year-old who still goes to a pediatrician? But seriously, folks, adults who remain in the care of the doctors who have cared for them since they left the hospital for the first time are more common than you think. Here are some reasons why.

1. They can’t find an internist where they live who accepts new patients and takes insurance.

Primary care doctors in their area may charge steep concierge fees or have a waiting list for new patients.

2. Their pediatrician may also be an adolescent health specialist.                                                                                                

These doctors are primary care specialists who have additional training focused specifically on treating the physical, mental, and behavioral issues of those in between the ages of 11 and 21.

3. They may have developmental or intellectual disabilities and changing physicians could be traumatic.

Adults with conditions like autism may have seen the same physician for most or all of their lives. Leaving their care may be a difficult transition that would risk upsetting their equilibrium.

4. They’re too busy (or lazy) to shop around for a primary care doctor.

If their doctor is willing to keep seeing them and they’re satisfied with the quality of care, why rock the boat?

5. They have a chronic health condition and a lifelong bond with their pediatrician that would be hard to break.

When a person has a congenital heart defect or another condition that management through adulthood, it’s comforting to stay with the doctor who’s been for them there since the very beginning.

6. They live in a state that offers the Children’s Health Insurance Program (CHIP), which covers them until age 19.

About two million kids have one of six chronic conditions that require regular care. These could include asthma, epilepsy, diabetes, attention deficit hyperactivity disorder or others. They are especially dependent on these programs, which vary by state. Their needs do not suddenly evaporate once they cross the threshold into young adulthood from childhood and adolescence.

7. They’re adults but not still quite “grownups” and aren’t willing to part with the familiar.

A recent poll from the Pew Research Center found that adults between the ages of 18 and 34 are still more likely to live with a parent than with a spouse or partner. The doctor they’ve always seen may just be another part of the landscape they don’t want to say goodbye to.