Here is a simple explanation of how easements and superelevation work and how to employ them on your layout to help your trains run and look great.
Easements are a factor most do not consider. Thus I am thinking that at least some troubles, such as derailments, may have a cause... I'll be looking at this video with good interest!
Honestly, derailments going into curves are probably most often due to very tight radius curve starting abruptly, a kink in the rail in the curve, or some other flaw in the track. Easements will, however, help the first two of these. I also find that someone who decides to take the extra step to use easements will probably be laying their track more carefully at this point that perhaps they might have when they did not. Like superelevation, easements are not essential to model railroad operations, but they don't hurt and they make trains look a lot better as the navigate the curves.
My post was probably not worded as it should have been. Meaning not that easements were a cause, but lacking them was a potential problem.
Cork roadbed is very handy for that. I superelevate by simply sanding one side of the cork--the inside of the curve. I usually stop too soon, but I find that a little bit is considerably better than none at all. But they're not only unrealistic in a yard, they can be a liability. Pulling a long string through a tight curve can result in cars coming off the inside of the curve, though that's not particularly likely except in extreme cases like old fashioned O27 and O32. Superelevation can make that worse. Anywhere trains operate at speed, centrifugal force prevents that from happening. So outside of yard limits, don't even worry about it.