I dont think this is something exclusive to bengal cats, most cats do this type of thing.
Unlike dogs cats dont have a loyalty to their owners, they are independant creatures who can be very selfish, and will quite willingly take up residence with other families, simply because they see an advantage for themselves in doing so,
Do your cats come home exceptionally hungry? Do they look as if they have slept rough?
Unfortunately there are plenty people out there who will take pity on a cat and feed it because they think they are lost or a stray, when most cats do have adequate homes to go to, but choose to spread themselves about