Too often we talk about hardcore vs casual players in an MMO from a content perspective. Raiding is for the hardcore, the main quest must be casual, form X of PvP is hardcore, form Y is casual, etc.
How you design your MMO determines a lot of this divide. Vanilla WoW raiding was certainly for the hardcore only. You simply couldn’t bring a lot of casual player to a raid and make progress. At the same time, current-day questing is very casual, with no hardcore option.
In EVE, the hardcore need the casuals, and the casuals need the hardcore. Goons couldn’t function without the top leadership (super hardcore), all of the Fleet Commanders (hardcore), the Special Interest Groups (SIG) leaders, etc. But all those hardcore players wouldn’t have nearly the same game without the hundreds and thousands of casual ‘F1 drones’ that also play and contribute.
Why someone is hardcore or casual varies greatly, but a well-designed MMO will not just accommodate both, but get them working together. An FC will lead dozens of pilots into battle, and while the FC needs to be highly skilled and knowledgeable, not all of the other pilots need that same level of dedication, which is much different than the above-mentioned raiding content.
The same goes for manufacturing; the hardcore come up with the what, how, and when, but they still need the line members to jump in and complete the orders, move the goods around, etc. Plus upward growth is almost always an option; if you want to get more into an area, and transition from casual towards hardcore, you not only can, but are often highly encouraged to do so. That’s not only good for the organization, but is also good for the game, as more involved players stick around longer than the average casual.