It should be noted that they both we created in a time before video games were widely available, so perhaps they are rather quaint in some respects today, but I think the fact that the skill required is different from that required by most video games today causes them to retain enough novelty to still be entertaining.
The author says that without the theme, Operation would be nothing but picking stuff up with tweezers. In fact, that is a game my siblings and I (all firmly in the Nintendo generation) enjoyed very much and spent many many hours doing (in a version called "pick up sticks").