There is conservative and then there is behaviour limiting on anxiety. As stated above, headwinds/tailwinds are factored in the RTOW tables or performance software.
I agree. If you ever use ATM/fixed derates, runway intersections, shorter runways when longer are available, etc. then your aeroplane is not performing as well as it could, in terms of absolute safety margins. But the ones you have are still adequate and acceptable.
The figures are such that if you go OEI at V1 with a wind component significantly worse than you used for performance calculations, it will still all work out. Most of the time the aircraft will perform better because of a lower actually density altitude than the one the sums used and gross/net differences. If conditions have changed radically since you ran the figures, airmanship would dictate you ran them again, if only for peace of mind?
I have no problem with “conservative” if there is a good argument as to why today is different. It’s like fuel: carry what you think you need but don’t just add it without thinking. Engine maintenance costs are extremely significant in modern operations and using more thrust “because I can”, not because it is required/sensible, is unprofessional.
If you feel the urge to pad out the numbers, where do you stop? When enough fudge factors have gone into a calculation, the result can diverge from what is actually needed by a silly amount...