Bittorrent clients and the need to open ports manually

Hello.
This post will not be in the form of an article, but rather in the form of a message to discuss the topic.
Everyone knows that Skype works great "both ways" even if the computer is not directly connected to the Internet. It is also known as it is implemented .
Question: why are there still no bittorrent clients that would work on the same principle? After all, everything is quite simple. Or am I wrong?
I will be glad to hear opinions.