Sorry. This will be a short rant. You have been warned.
Why do we still put up with the telephone?
Why don't I like being phoned?
* Of all the modes of communication, it is by far the most intrusive.
* Most phone calls could have been an e-mail, with screenshots, facts, and numbers in it. On the phone, the caller has to read it out aloud, and I have to write it down. That is not efficient.
* As a company, you are expected to “pick up” the phone, and even need to hire special people for this, be it a receptionist or an entire helpdesk crew. But for small companies and small teams, this is a heavy burden.
* The mental load of context switching costs a lot. We work less efficient, or more slowly because the phone rings, and after you put the horn back, what were you doing? You need time to pick up the work again. Before you get to work, the phone rings again, and you are once more not doing what you were supposed to be doing. It looks like the Greek myth of Σίσυφος who was condemned to push a rock up a mountain but never reach the top, forever.
Why don't I like phoning up a company?
* Rarely do I know whom I need to speak to. Much rather do I send a mail that can internally be forwarded until it reaches the right person.
* I have no way of knowing if I'm disturbing a person in his work. By calling, I'm implicitly demanding his/her time right now.
/rant
So this: "By calling, I'm implicitly demanding his/her time right now." is just a projection of your own opinions of phones onto someone else. Likewise not knowing who to speak to - you call, let someone answer, tell them what is up, and let them point you to the correct person. No biggie. It is how communication worked in days of yore.
I'm not saying you need to change your attitude about phones - hate them all you like. But not everyone agrees with you, so if you sincerely are wondering why phones still exist, it is because different people exist.