I would not say it is a requirement. Just some insurance for protecting your investment, it is nothing more than a suggestion. I have managed lugging around a Mark III combo amp for years, no case but wish I had one. Much heavier than the Mark VII combo by at least 10lbs. The Mark III had an EVM12L Black Shadow speaker so that added some weight to it.
Just pointing out that when you travel to various places, egress may be difficult with some amps to carry into the establishment. I heard of the stories but never experienced some of the issues many have encountered. Combo or head with cab will still have its challenges. Probably does not make much of a difference. Not like you can carry the amp in one hand and the guitar in the other as that may not always work out.