It's less about adaptive value or not and more about body plan.

Your basic tetrapod body plan is pretty lizard-like (in turn, it's very basically a fish with four legs stuck on). The key thing about this body plan is that the main axis is horizontal. Makes sense, after all the ground is horizontal and that's what you are moving across.

Most tetrapods, heck, most vertebrates keep this basic orientation (for exceptions, see seahorses). Swimming, flying, walking, the body tends to be held horizontally. And this goes for bipedal movement too, which is actually pretty common. If the hind legs are longer than the front legs, and the animals has a big tail (like most tetrapods), it's pretty easy to get up on two legs. Tends to happen in lizards when they run, they are essentially just popping wheelies. Loads of dinosaurs also went around on two legs, with the body horizontal and the tail out behind for balance.

But this doesn't really work with most mammals, which tend to have piddly little tails and long front limbs. Which is why you rarely see any sort of bipedal mammal.

Now like I said, most vertebrates go around horizontally. What's an exception? Stuff in trees. Climbing, hanging from branches, that often puts the body vertical. And requires good balance too. Various primates will go vertical and even bipedal in trees, running along branches and doing that sort of thing, or swinging and leaping around upright.

When we get to apes, you have no tail at all, so there's no hope of going around horizontal-bipedal like a normal tetrapod. But Gibbons like to spring around in trees, run along branches, and walk upright quite a bit when forced onto the ground. Apes that spend less time in trees need to get around more efficiently. Chimps and gorillas seem to have adopted knuckle walking, hominids seem to have improved the original upright stance for efficient use on the ground.

But it's only the odd confluence of lack of a significant tail and preexisting history of upright orientation that makes upright movement plausible in hominids.

As for penguins, you'll note they also lack significant tails and (unlike most birds) have the feet at the very rear of the body to improve swimming efficiency. Which also leaves them stuck with no other options.