These older Sifu accepted these challenges because they could! They truly did have skills and were not afraid to 'be tested.' Try that these days on one of these cream puff 'masters' and I bet they block with their face...or run away crying for help...
First, let me point out that I am a huge fan of any senior martial artist, be they modern or historical figures. My comments are designed to open up a dialog, based on my personal experiences and travels throughout Asia and the West (relating to this subject) and not an attempt to insult or diminish the skills or reputation of any martial artist.
Let me "jump start" the thread by saying that most people doing the "challenging" (fighters are also people) are handicapped by their own lack of confidence, and the "master's" reputation. The "master" has a huge advantage because he controls the mind of the challenger far more than the challenger or "master" realizes.
Think about how some modern "masters" are able to "knock out" their challengers-in-demonstrations, without even touching them, and how the verbal build-up prior to the knockout, along with the other staged preliminaries add to the master's "advantages".
Project some of this "hype" and "mind control" to the challenges of old and you get insight into where I'm going with this thread.
What do you think about this whole subject of certain old (and generally dead) martial art superstars?
Were they just a little above average fighters, when compared to other fighters of the time or do you believe that they actually deserved the "superhuman" status given to them by their students?