Some cats just dont like going out and when Misa and Sasa aged 4 and 6 came to me they were kept in and when I opened a door for them eventually, they ran to the other end of the house in fear, although they spent weeeks sitting on the window sill looking into the garden.
Sasa had been living in a cage at a rescue for over a year and Misa had been saved by a vet from being PTS but had been locked in a shed. Sasa however lived with ferals before she was caught by the rescue and is still semi feral and is now scared of being shut in anywhere!!!!!
My two birmans have access to outside but dont use it very often and apparently were used to going out before I had them, mind you they are older cats.
I would never force a cat to go out and if they didnt want to I would let them stay in.