CPU IHS lapping - why isn't it done from the factory?

So, as the thread title implies... what is preventing manufacturers from creating CPU's with IHS's that have been pre-lapped?

Right now, both Intel and AMD are producing CPU's with IHS's that are... uneven at best.
In Intel's case, their CPU's are suffering from using a questionable/lousy thermal paste on the CPU die.

We probably know that in some cases, doing away with an IHS alltogether might be a better idea, however, as Ryzen demonstrated, it can be implemented properly... but in that case, wouldn't it be better to ensure the IHS is as flat as possible and has a mirror finish on it's surface to enhance cooling?

 

@Deks greedy corporations are always happy to save a few cents on each unit, any way possible - especially when Average Joe doesn't care anyway.

 

I know how cost efficiency works, but corporations are obviously taking it to the extreme and are cutting too many corners for my liking when it comes to cooling designs (and are still using outdated cooling methodologies for laptops in general because they can't be bothered to implement better techniques that existed for a while now).

The average Joe not caring is rooted in education and general mindset of use and discard mentality.
Think of how much better we'd be better off if laptops were designed with efficient cooling (Even thin and light ones) and modular hardware that can for the most part be upgraded/replaced with better versions over time.

Lapping can improve thermals in various situations, and obviously, you want to avoid unnecessary problems down the line by ensuring you made a product that... works as intended (not just barely with high temperatures that skid on the edge of system shutdown).