As far as I know, the internal mechanism parts of the lock cylinder are made from zinc/brass and when this part develops problems spraying a dedicated spray (based on PTFE) through the keyway usually solved the issue.
But are lock cylinders (internal mechanisms) lubricated in the factory, or the internal mechanism part (like the pins and bores) are just polished very well in the factory, so they don't need any lube as they made from brass or zinc?
The pin cylinder -- the part that recognizes the key, bored shell and plug with pins and springs -- is typically brass and so does not tarnish significantly in any but the worst conditions. It may or may not have a dry lubricant applied to it, either graphite (traditional) or more recently a PTFE "dust" lube (some of which apply as a liquid but the carrier evaporates away). The cylinder can experience wear, but it generally takes a significant amount of time, and some of that is unavoidable and simply requires rekeying when the wear gets serious enough to affect performance. If a lock starts behaving like it's sticking, LIGHTLY adding more graphite or teflon dust (a "puff", not a pile!) may help.
The latch mechanism (the part that actually holds the door closed) is often steel, and may be given a light coat of grease to protect it. Since these are large parts, they don't often seize, but they too can wear out eventually.
They are lightly lubricated to prevent oxidation.
The lube helps the workings also, but the primary reason is so the metal components do not degrade during shipping/ storage.
It always helps if a little lubrication is applied during installation into the door.
