Japanese syllables are often shorter than English syllables, and a native speaker can articulate then quickly and fluently, but it seems to take much more linguistic "mass" to say a thing in Japanese compared to its English equivalent, unless you use a blunt direct form.
Listen to some spoken Japanese; you might find it sounds a lot like Finnish.
Also in college every single one of my Japanese friends had a business keigo book they were constantly studying in their senior years to prep them for communicating in the working world.
German: Was ist das? (3)
Japanese: Are wa nan desu ka. (5)
And this is just a simple example. Often the sentences get even longer when set in past tense or in some of the "politeness forms".
Maybe that's the reason they use these symbols, they allow for compact writing of even long sentences.
On the other hand, the Japanese I met didn't really "talk" the way I learned it at university. Noone said stuff like "Are wa nan desu ka", they just said "Are wa?"