Saying Hi in DF is a bit unnecessary since the idea of DF is to do a Duty and leave, unless you see a bonus there really is no need to explain anything or have to see if people know what they do cause the idea behind the whole search function of the DF is to find a group, do it and leave.

But see, this isn't the fault of the player, it's the fault of the design, the act of communicating with players cross-server is lost because there is no way to stay in touch unless you make a char on that server for some reason but even then, there is no guarantee you will ever be grouped with them again.

The social aspect of DF could be improved with a cross-server friend list where players could meet, find players they enjoy playing with and have a way to play again but since this isn't possible, the idea of socializing for a short time with someone for less than 5 mins total if that just seems not worth the time when the odds of running a dungeon with them with the current design of DF is rather low.