Insurance companies have the right to reject new clients without giving them a reason to why they are being denied insurance here in Europe. In addition most private insurance companies do not insure against pre-existing conditions. I know because my partner survived cancer three times and getting private insurance here was impossible. 

https://www.nytimes.com/2018/04/03/technology/grindr-sets-off-privacy-firestorm-after-sharing-users-hiv-status-data.html