etiquette

Let's talk a little about cell phones. Now, in the States we have a somewhat-debated, not-always-followed, idea known as "cell phone etiquette." The underlying premise is that it is not polite to talk on your phone around other people, or even to let it ring. That can be debated, and there are exceptions. But in class, in church, at public performances, etc, you are supposed to turn off your phone, but if you don't and it should ring, you are required to silence it as quickly as possible. The ringing alone is enough to prompt dirty looks at the least, and comments or expulsion from the room at the most.

This, however, does not apparently hold up in Russia. They seem to have no discernable cell phone etiquette, except perhaps what I would call "be sure to answer your phone whatever the circumstances."

Cell phones ring all the time in class.
Students usually answer them.
It is typical for the student to bend over double at the desk, hoping to hide behind other classmates, and say in a low voice, "I'm in class now, I'll call you back."
Other times the conversation lasts longer.
At least two of my professors have answered their phones during class. "Sveta, I'm lecturing right now, I'll call you back." One professor's phone rings every week.
One time, a girl came into class at least twenty minutes late, while the professor was lecturing, walked down the middle of the room to the front and plugged her phone and charger into the wall near the professor. Audacious.
Texting during class is nothing. I do that.
Some students get up and leave the room to answer their phone. I guess that is okay.
A phone rang in church and the same thing happened - the person ANSWERED to say they would call back. Oh my. I suppose that a reason for this could be that people here don't have voice mail. But it seems to me that they could just text the caller and say they can't talk at the moment. That's what I do.

I just don't understand.