I don't think it is "cruel". It's the matter of opinion.
As for what to do with dogs when you are away for a very long time.
Some people can afford to pay people to take care of their pets while they are away, although the quality of such services can be vary.
Some people have friends or neighbors who can take care of their pets while they are away for free. The quality of such care can be vary too. As some people will do no more than feeding, while some other people will actually spend time to walk your dogs and even playing with them.
Some people simply do not have any option at all besides having someone to come over once a day while they are away. Not everyone have trustworthy friends who can take care of dogs for them.
