Kat and Rumble don't buy Luden's because its an early purchase focused around mana and they have higher priority buys. This is actually one of the worst examples you could give lol.
People buy Luden's because they NEED mana, and it has a LOT of it.
Rumble doesn't need CDR much. He builds up too much heat then. Kat doesn't need CDR much. She has resets and is focused around burst.
RoA is still the best AP stat-stick, no matter how you look at it. 135% efficiency is absurd. I wouldn't recommend it on Morde, but still.
Its PASSIVES you're looking at and in many cases passives outweigh a good amount of stats. Buy for passives and needed stats, much like Yasuos used to buy Trinity Force, even in pro scene. Its happened with Lee Sin too. AP Tryn.
In most cases mana items are not worth it because you're putting yourself at a 400ish gold deficit, but sometimes its worth the stat-line, mostly in regards to armor/mr, if you've already purchased your primary options. Otherwise if a passive just synergies far too well with the situation.
If you have a lead you have more room to make these kinds of purchases, but that is obviously a trade-off you have to weigh, and often there are passives you already want on items that don't have mana.
That doesn't make these purchases wrong, it makes them less preferred, especially when you take into account slot-efficiency and end-game. They aren't going to lose you the game unless you aren't buying them for the right reasons, as uncommon as those reasons may be.
The car example makes no sense. People do that anyway.