Maybe someone can correct me here, but I think we're moving into the future where most components won't be marked at all. These days I'm seeing ever more often even basic things like SMT resistors without any label.
Most device vendors actually don't want the markings on components: they make reverse engineering of their designs easier (you commonly see markings on key chips scraped away because of this).
For vast majority of electronics, component-level repair is not done anymore. Even for expensive devices it's cheaper to replace the whole failed assembly than pay someone to hunt down the failed component. So there's no benefit for service engineers either. Manufacturing is all done by machines where you only need to identify reels, not individual components.
In this view, markings on components are just an unnecessary cost for all parties. I'm not happy about it because it makes electronic things even more unserviceable after they are no longer supported by the manufacturer, but I think all incentives are in this direction.
For something that has already been produced for some time, the markings may be no longer useful for the manufacturer.
However the first batches of boards for a new design, or after some design changes of an older product, frequently have assembly mistakes resulting in obscure bugs that are much more easy to solve when the devices are marked.
This is one of those things that Google and other search engines have gotten increasingly bad at finding. chip.tomsk.ru was my go-to for looking up SMD markings before it sadly disappeared a few months ago.
Man, I wish I would have known about this a few weeks ago when I was working on repairing a water damaged controller board from an electric smoker. Fortunately, the damaged components were not the mysterious SOT-23 devices labeled only "S3", but just a couple shorted-out diodes. Without this page, it would have been quite frustrating trying to source a new "S3" were it blown out, as I wouldn't have been able to measure polarity or hFE to narrow down a short list of candidates.
Great resource - but needs clickable package type names so you can check the outline of the case, or even ID to datasheet links.
Ability to search by case type and function would be great - often you can't read the marking but you can make a good guess at what a device might be doing - "what could this SOT-23 voltage regulator be" etc.
This is an excellent database, however it's still limited in content, maybe due to the likely source of scraped datasheets. I've yet to find ANY information regarding Great Wall Semiconductor's AB5603 in 36 pin chip scale BGA package, as well as devices inside "vintage" oscillator modules like "AF1U" and "AF4S" in SOT-23, as well as Seiko NPC "0709 010K1" in SOP-8.
Unfortunately many datasheets don't include short codes for the devices they describe. And manufacturers often hide them behind search submissions. Hope you can figure out who made the part you're looking at AND that the totally-still-in-business company has a lookup tool!
Most device vendors actually don't want the markings on components: they make reverse engineering of their designs easier (you commonly see markings on key chips scraped away because of this).
For vast majority of electronics, component-level repair is not done anymore. Even for expensive devices it's cheaper to replace the whole failed assembly than pay someone to hunt down the failed component. So there's no benefit for service engineers either. Manufacturing is all done by machines where you only need to identify reels, not individual components.
In this view, markings on components are just an unnecessary cost for all parties. I'm not happy about it because it makes electronic things even more unserviceable after they are no longer supported by the manufacturer, but I think all incentives are in this direction.