I am aware that this behavior has been around since CMANO. I have been perplexed by it for that long as well.
For example, in the scenario "Operation Opera", the Israeli attack on the Iraqi nuclear reactors, the Israeli F-16s race into Iraq with the mission of killing the reactors. Most of the SAMs are really old. Some have 0 percent chance of hitting the F-16. Almost all have less than 6 percent chance of getting a hit. In fact, most have somewhere between 1-3 percent chance of hitting anything. So, it would appear that the F-16 should pin its ears back, head straight for the target, release its bombs, and head home. Instead, at the first sign of a SAM, the F-16 begins evading. (I realize that I can turn it off, but you would think that the computer could do some extra calculating to determine if it would be a good idea.) So, as an endless number of SAMs are fired, the F-16 keeps turning away from the target, and evades missiles that have little to no chance of hitting anything. The longer that the F-16 stays in SAM territory, the greater the chance that one of these SAMs will get a dice roll of 1, and actually hit the F-16.
Continuing with the scenario, the SA-6s are a real threat to the F-16. Unlike the other SAMs, the SA-6 has a really decent chance of scoring a hit. So, the automatic evasion is actually needed when the SA-6 is around, but not the others.
But, right now, it's an all or nothing thing. You either turn it on so that you can possibly evade the SA-6, but you will also waste all of your effort running from all of the rest of the SAMs, OR you turn it off, thereby ignoring the other SAMs (they weren't going to hit you) but make yourself at risk to the SA-6 wherever it is.
What I would like to see is some kind of risk meter. This would tell the plane that if the risk is less than X-percent, then do not evade, but if the risk is greater than this, then do evade.
Think of the WWII movies. Flak is everywhere. Well, if Flak was everywhere the B-17s would constantly be turning around evading and they would never reach their target with so many attacks occurring. In real life, they raced forward.
In this scenario, I used just two F-16s, turned off the automatic evasion, and raced toward the target. I killed both reactors, but was ultimately killed by the SA-6s because I wasn't evading. So, it would be nice if you could do whichever was needed to accomplish your mission and survive. Evade the SA-6s, but ignore the others and hope and pray for your safety.
It's just a thought.