Whether an employer should select employees who have a personal interest in their field of work very much depends on what the job is. In some cases a personal interest matters, in some cases it does not. To address your specific scenario, yes I would select marketing people who have some evidence of a personal interest in the field. Marketing is something that is done better when the practitioner thinks about it. For other jobs, personal interest might matter less.

As for software developers, I think most employers do not expect to provide employees with learning time. Larger employers do so, typically through formal training programs.

But if you are a software developer then you need to understand that the industry as a whole expects that you do your own learning. What do I think? I think that is fine, it's no great burden to put a little attention towards software development outside work hours. Doesn't need to be all your available time.

And if you want to be a software developer and resent learning and the time it takes then matey boy, you are in the wrong game.