Some people would argue it is cruel to keep cats inside all the time whywhywhy? How do you go against nature? Dogs are different animals altogether. Of course a few cats may be happy to stay inside for ever - others would be climbing the walls!
To me IF you want a house pet, people should consider budgies, rabbits, guinea pigs, fish but not cats specifically. If you manage to find one who is happy and content indoors - so be it - but it isn't the norm. Cats are free agents and need to explore their surroundings. It has nothing to do with 'taking responsibility' It has been like this since time immemorial.