That's an easy question (and its corollary is: why isn't the data accurate in all cases); if they did have all that information then they would charge a great deal more for the database. Of course they would also have to stand by it and prove the values were accurate.
Best to build your own set of data in your own material database with values you are comfortable with.
In response to above,
I too face similar situation often, when I select existing S-N from Database; it could not cover entire range of my cycles & hence would not be appropriate to use even existing S-N.
Can you suggest some links/papers/pdf's here to fetch S-N for Steel materials please ?
I'm curious... it seem to me that you can't input your own S-N curve. What package of Simulation do you have access to? Pro? Premium?
I can input my own values, I am using SOLIDWORKS premium package. The problem is it seems that if you need to do a fatique study you must input your own values for most of the materials S-N curve. the question I had was why isn't this build into SOLIDWORKS materials library.
Maybe to make them safe as James Riddell said,
if they did have all that information then they would charge a great deal more for the database. Of course they would also have to stand by it and prove the values were accurate.