Consider the fact that Stormtroopers are essentially soldiers, and when they're all in formation to greet the Emperor, they had better look all nice and tidy. I really don't think the Emperor would have been pleased with ugly unsightly bumps, dings, cracks and unsightly paint lines.
If you want to go uber-anal and go uber-screen accurate, then some TK's had velcro straps sticking out; one TK had some white rectangular patches on his armor, and one TK had his handguards worn upside-down. So all you uber-analites out t here: these flaws were all visible in the ANH DVD, therefore they're "screen-accurate", and unless you reproduce all those mistakes, your "screen-accurate" armor is in fact inaccurate!
Rather, a movie production follows a hectic schedule. Back in the old days it was okay to cut corners because a lot would not be picked up on camera. When the Star Wars special edition came out, and then the HD versions came out, we can see the results of digital resolution enhancement.
In other words, we are watching Star Wars at higher resolutions than what was possible back in the days of celluoid film - even on a large projection screen! Why do you think the ROTS helmet was made to such a pristine level? It had to survive closeup shots moreso than the "Hero" helmets of 30 years ago. Personally, I think even Vader's ANH paint job was just a very bad paint job. But anal fans have decried, "It's battle damage / wear and tear" and seek to reproduce bad paint jobs.
Okay, go for it; more power to you. But how can Vader have experienced any battle damage when all the stormtrooper boarding party killed the rebel soldiers PRIOR to Vader boarding the Rebel Blocade Runner?!
One fan argued, "Well, obviously Vader got that battle damage earlier on before the Tantive IV sceen." EXCUSE ME?! We're talking about the Dark Lord of Sith here who, in ESB, could block frickin' lasers with the palm of his hand. You're going to tell me that lasers or physical objects are going even get a chance to come close to Vader to even scratch or ding his helmet and facemask?
Truth be told, the bad paint job does add to the distinctive aesthetic of Vader's facemask, hence at some point I do want to reproduce it myself. We are, after all, in general trying to reproduce how the prop looked on the silver screen -- not how the prop looks like in real life.
I've also seen many tutorials of people modifying their Rubie's helmets, only to find that after touting their mods as "screen-accurate" the results failed to address the fact that the helmet still looked ugly and misshapen. But I guess that's why they bury it under a boatload of gloss black paint and add "Reveal" neckbraces so that people get distracted by the bling.