Typically, it is for followers. I had one teacher explain that "surrender" means the lack of intention. Another said something like, she allows the man to lead, without a lot of extra "noise". Now I'm not one of these who claim there is only one way (or philosophy) for people to dance tango, but that's what I believe some people mean by that term. For people who are dancing primarily for the embrace (as opposed to for the steps), it's a good philosophy, IMO.