Words have recognizable shapes. The shape and context of the word impacts meaning, legibility, and memorability. The assertive block of upper case. The rise and fall of ascenders and descenders in lower case. Shape emerges from font, but has some unique qualities that merit as separate discussion.
Shape has some context-specific considerations. When you are driving at 75 mph you want the highway signs to be in sentence case. You can recognize the shape of the word before you can actually read the letters. It helps you process the information and get back to the important work of speeding.
Sentence case tends to be better for blocks of texts, too. The visual cadence makes it easier for your brain to process more quickly.
A good, but surprising example is Marlboro. The shape of the word is distinctive apart from the meaning derived from reading the word. And they know it. Marlboro was a prominent sponsor of the Ferrari Formula 1 team. But when the EU passed a ban on cigarette advertising on the cars, they were faced with a unique challenge. However, had a unique asset. The word is so recognizable on packaging that you don’t have to explicitly spell it out, you just have to evoke its shape. They replaced the word on the car with a graphic that looks like a barcode. At 200 mph it also happens to be recognizable as the blur of the wordmark.
Interestingly enough, we have been asked several times if we use the Marlboro font. The fonts aren’t close, but the shapes of Marlboro and Bullhorn are similar. Side by side no one would mix up the two fonts, but with distance the shape makes a powerful impression.
There are also contexts where upper case makes sense. The blocky nature of the shape requires more attention. That is why it works well with headlines and ad copy. If the person takes the time to read it, it is more likely to stick because it required more of their attention. It sometimes works for naming depending on the goals of the identity.
Shape is a component of language. Language conveys meaning. Meaning is impacted by shape. It is like a zen koan, a snake eating itself. Paradox. It is complex. It is something that you should understand, but not something you should worry about. That is what we do.