There's a bit more at play than just shyness here, I think. I've sent texts a number of times just because I didn't know what the person was doing on the other

There's a bit more at play than just shyness here, I think. I've sent texts a number of times just because I didn't know what the person was doing on the other side. Calling someone for a chat in the middle of the day is pretty disruptive, especially if they're at work or somewhere where they may not be able to talk loudly (library, movie theatre, open office layout). When you call, you don't just have to interrupt the person you're calling, but you could be interrupting everyone around them too. At least with texting, you can more or less assume only the person you're texting will have to pay attention to the message, and even then they can delay reading or replying until they have sufficient time.