I would have thought exactly the same as you, OP, if I'd seen it, but then, as PPs have said and going on some of my own experiences, you can also see why they do it.
There can be a huge disconnect between what different adults do and don't know. Sometimes it's down to basic intelligence, but it can be down to all kinds of different factors - background, parenting, school attendance, social circles, whether or not people read or watch the news. My in-laws are older people - both very intelligent and highly educated, but they wouldn't have a clue what basic internet terms meant. I'm sure there are things that are stinking obvious to them which I would know nothing about.
I sometimes compile community quizzes, aimed at a wide range of abilities and different backgrounds, but I'm still shocked at some of the (what I think are) silly easy questions I include for a bit of fun (or to use to shoehorn a joke in) that still baffle certain of the adults there. For the last one, I'd done a couple of separate rounds for the younger children, so that they wouldn't feel excluded; but in truth, some of the kids would actually have known the answers to several of the 'adult' questions that some of the adults were stumped by. Then again, one of those adults is a mother of five children, whose husband works away during the week, and she keeps their household running smoothly in a way that I could never begin to imagine how to do myself.
I suppose the BBC is there for everybody, so they need to cater for all levels of ability and interest, but it's an impossible balance to strike perfectly, not going over the heads of the least able and leaving them uninformed without making the most able feel patronised and insulted.