Which "they"? JJ rebuild kits, track bars, new complete JJs, ...?
Like I said, neither end of new trackbars had any grease. And at least 1 of the 4 TB JJs had a 1 piece race, not 2 piece. So the only way I know to grease that style is through the zerk after drilling through the race.
JJ rebuild kits do not come pregreased. That's probably a wise decision.