Component level repair on modern phones is virtually not done at all.
The chips are highly integrated proprietary components anyway, you will not be able to get legitimate replacements. You may get them used, but the major chips, at least on apple phones, have serial numbers that need to be verified by apple. You cannot just swap a chip and expect the phone to work.
So there is no reason to wipe off part numbers. A replacement will not work anyway.
And for less integrated stuff wiping off part numbers may delay reverse engineering, but will not stop dedicated attempts.
So it would be an additional process step that needs to be paid for that has little benefit.
As a manufacturer, you might also want to be able to repair stuff yourself. If you gunk up the phones, replacement is the only option, often way more expensive than module swap for, say, a broken camera.
And again, gunk costs money

For Apple devices, the replacement modules are fully under control of Apple. For the longest time it was absolutely impossible to get genuine Apple replacement parts. And third party parts are often deliberately crippled, since they fail the DRM security checks. You can now get genuine Apple parts. For a similar price as that repair would cost at an Apple store. So disregarding logistics cost, Apple may make more money on a part than on a repair.
And finally, there is still some kind of reputation attached to repairability. That may not be important to many customers, but for some it is important. And there are increasing demands to essentially outlaw deliberate attempts to make repairs more difficult or impossible.