Ah, consistency. Consistency is it's own reward, it helps to maintain fairness, and more than a few players have been saved from low rolls, that simply did not count, though, because I am consistent, it has also more rarely resulted in a high roll being "wasted". There is also the benefit to keeping people who are prone to cheating from doing so, though I feely admit that is not really of much concern to me at this point in my life.
Hmm, as an example, let's assume you know without question, that you will be using the aforementioned investigation, will you be using intelligence, dexterity, or perhaps wisdom? All might be appropriate depending on what you are trying to determine, and what method you are using to do so.
I suppose I can turn this around. What is gained by making a point of pre rolling a die that you don't know that you will need, you don't know what modifier may be added to it if yp u do, and that you know makes me stop for a few extra seconds, while I get myself back on track, to tell you that you didn't need to roll, that you automatically succeed, but, due to examining the alien device, I DO need you to roll a d6, to see if you activated something on the alien device on accident while you did so?
The trick to all this, it is not about my rule or the highway, so much as this is the process that I use to bring the best game that I am able to run by using my process, why would you not respect that this is how our particular table works, any more than if your die falls to the floor, it gets picked up and rerolled?