They're 65 and 75 right now. (His birthday has already passed, but hers hasn't.), so they would've been roughly 40 and 51 when they got together.
I'm aware of the differences, in either case, and I'm not saying that an age gap has to be the only source of those differences. Frankly, I think differences based around culture and hobbies/interests are the best ones, as those are more likely to get both of you to try new things. That said, there are positive and negative aspects to your example. I mean, unless I'm wrong, you seem to view the younger person's lack of experience as some sort of downside that somehow puts these two people on uneven footing, possibly insinuating that the older person has some sort of unfair advantage over the younger person, whereas I'd argue that the older person who has more life experience and relationship experience could offer a lot to someone lacking in both. If anything, the older person had a "head start" in a sense, but that doesn't mean that the younger person is necessarily any less emotionally mature, and the younger person is arguably at an advantage should they happen to want the sort of guidance a more experienced person can provide (assuming said more experienced person isn't a sleazebag, of course).
Yeah, life is hard when you're young, and there's a lot of new stuff that's very scary and stressful to deal with early on. In some sense, wouldn't having a more experienced person around be helpful? Sure, you could just say to that younger person, "Oh, ask your parents." What about someone who maybe didn't have the best upbringing and wouldn't trust their parents for life advice any farther than they could throw them? Some people would cry "daddy issues" or something, but there's something to be said for having anyone who's accountable and reliable around, and - with us being creatures of habit - we tend to seek those traits out from sources we THINK are reliable sources for them. That doesn't mean you NEED an older person if you're younger, but I think a lot of people seem to think that way, and it seems to work out in many cases, judging by the number of relationships with significant age gaps you see. Sure, two younger people may seem more "compatible" because they grew up around the same time, but there's absolutely no guarantee of compatibility there. You've just got two inexperienced people facing the same problems the couple with the age gap was, but the couple with the age gap has more collective experience, while things are more "acceptable" to the masses with the younger couple because of the lack of an age gap. It's an odd standard to hold.
I'm not saying that everyone should shoot for a relationship with an age gap, but I do think there are people who've had some pretty rotten luck and could benefit from stepping out of their "comfort zone" a bit with regard to certain things. Again, age is just one of those things, and you clearly can't expect more maturity from someone who's much older 100% of the time. That said, people have this weird way of working within certain confines when seeking out a life partner. With life largely relying on healthy compromises, it's just strange to me that some people are so adamant in trying to find the "perfect" person right out of the gate as if they were shopping for PC with certain specs when compatibility really needs to be a long-term thing you work on.