@Ceci03
I am on the fence here. OTOH your OP sounds a bit callous and harsh (like you're annoyed by your parents just being ill!)
Then again I get what you're saying. Who wants a life of going to hospital appointments several times a week?
Maybe they like going/enjoy the attention? Who knows?!
Some people love the attention they get from being ill/going to hospital/being in hospital.
One lady I know is around 75, and has FIVE carers a day visiting her, (for about 45 minutes each time,) 7.00am-7.45am, 11.30am-12.15pm, 3.30pm-4.15pm, 7.00pm-7.45pm, and 10.00pm-10.45pm. The first one gets her up out of bed and showers her and gets her breakfast, and the last one gets her supper and puts her to bed. The ones in between, clean for her and cook her meals, and change her (adult) nappies 4-5 times a day. She doesn't leave the house to even go in the garden, let alone go to town, or for a walk around the village.
She has 4 kids who each visit her once a month if she is lucky. Apart from the carers, she is alone 95% of her life, watching TV, and waiting for the next carer to come. She regularly falls over, she can't go to the loo on her own, or shower or wash herself, and she is locked IN for her own safety.
Everyone around her (neighbours and acquaintances and people she knows) thinks the same thing... WTF is the point in living? It may sound harsh (to some,) but seriously?! What kind of life is THAT? 
The same could be said/asked of your parents (and people like them.)
What is the point of a life where you are constantly ill and in hospital and having treatment, and battling pain, and pumping yourself full of drugs?
If were an animal, they would be put to sleep. Does make you wonder why humans go through what we wouldn't put animals through...........