I suspect the answer will be close to "because it increases social welfare"
Ok, now what's the evidence that this is in fact the case?
To a first approxmotion: the fact that there's uptake for it means people judge it to increase their welfare.
Since that is obvious, I suppose you mean there are negative externalities that lead to ne.tt negative welfare. In which case: what is YOUR evidence?
Suppose I told you that I knew for a fact that the following statements were true:
You’d think I was crazy, right?
Now suppose it were the year 1901, and you had to choose between believing those statements I have just offered, and believing statements like the following:
Based on a comment of Robin Hanson’s: “I wonder if one could describe in enough detail a fictional story of an alternative reality, a reality that our ancestors could not distinguish from the truth, in order to make it very clear how surprising the truth turned out to be.”1
1Source: http://lesswrong.com/lw/j0/making_history_available/ewg.