How is that different? It's one thing when you both prefer to just sit and talk. I'm talking about when someone corners you and talks your ear off.
About the differences. In ballroom parties, in general, people come to dance. It is encouraged to dance and switch partners as much as possible. The social norm is to be inclusive, and circulate. It is considered impolite to decline an invitation without a very good reason. In milongas, it is not the case. I would say it is somewhat the opposite: one needs a good reason to ask or say "yes".
Hence, the question of a newcomer from other social dances background: "I go to a venue. The leader-follower ratio is good, I look and behave nicely, I do not have two left feet, I introduce myself around, and still some people do not ask me. What is wrong with the picture? What else would it take to get dances?"
What I am trying to say that in milongas and practicas at times it takes much more because the group dynamic might be more complicated. Some people did not come with an intention to dance or did not intend to circulate (much). I may go to a milonga to listen to music, drink a glass of vine and chat with a friend who just came back from a trip. In some dance parties it would be rude and unsocial to behave that way, in a milonga it is perfectly fine.
Of course, in tango communities there are also people who like to circulate a lot, to welcome newcomers. But it is good to be aware of different tendencies, not to take some things that are going on in a milonga personally, and make them discourage you. Although it might not be easy at times.