And again.. missing the point. Level restriction IS a restriction on content--by definition it restricts you to a lower level content level than you otherwise would be without it. This can and typically does lead to a great deterrent for those that have moved on to a certain stage of the game. IT IS ALREADY HAPPENING TO SOME DEGREE AT i110.
Personally, I haven't touched anything below High roulette since the first week of 2.5...and that was only until I unlocked expert. Now I just run that once a day for the tomes and alex map, then I'm chasing lights and Alex/materia for my second weapon until I complete their current stages. Once I'm done with my relics, you may not see me an anything but Expert and CT chains--and that may only hold until I'm done with the Ironworks gear I want. I could care less about glamours, so once I'm done with older content... I'm pretty much done with it unless I desire to help someone run it. I'm pretty sure I'm not alone in that regard. Stepping into a fight with nerfed stats is NOT an incentive to do so, and no.... tomes are not a valid reward to sway me either.
It is not a new problem... I watched it play out to the point where there was about a 40 level gap in content participation with XI playerbase a few years ago, and the only thing that ultimately revived it was to uncap the content. It creates a REAL problem with balance when you clamp down too hard with the level cap until you either manage to create a mass influx of new players to pick up the slack and fill the void left behind when the bulk of the players move on, or you uncap it so that those older players don't mind so much assisting them (or gives them a sandbox to play in for sh!ts and giggles). We've all seen how well SE markets their FF franchise...people aren't exactly standing in line to buy the game, so there may be a problem bringing in enough new players to fill the ranks and keep older content relevant. We've already seen a steep decline in participation at the lower end of the content scale---the only reason some of it gets done in any manner of regularity is because people that want to finish the relic track or Ironworks and such HAVE to do it until they get their KI's and mat's to upgrade. Chances are, once they're done with that requirement, they will be ready to move on to the next new thing and leave the old stuff behind them until someone they know needs help.
Which brings us to Mykll's point further down about SE forcing people back into older content as needed via the relic chain. They risk pushing the players too far with that cheap and annoying gimmick to the point that they just stop doing it. Myself, I'm making two...simply because I started them and want to finish what I started. Every other job has a UAT weapon until I acquire something better as a drop or as a purchase with tomes or whatever method is made available in future content. Granted, I have some RL friends that left the game a while back, and if they come back I will queue with them to help THEM finish their lines, but that may be the extent of it unless it is something to benefit an FC member... but I don't plan on queueing them in DF just for the sake of doing it at that point. I am sure I am not alone in that regard.
It really is that simple. If they push the players too hard with this backwards mentality of forcing them into outdated capped instances to continue piecemeal advancements on their gear, but there is an easier option available that is just as good, or maybe not quite so good but good enough to complete new content (or, shudder the thought, a weapon BETTER then the potential new relic stage)---eventually they WILL stop advancing the relic quest line completely and just move on to the next new shinies made available as a drop or purchased with each new content release.
And... once again, looking back at XI. We saw the EXACT scenarios play out with that games artifact, relic, mythic, magian, and empyrean lines. They figured out there was far more easily attained gear that was good enough to use in the new content. Only the die-hard min/maxers went after the more highly specialized modifications at first, but eventually those got left behind too for the new stuff in the expansion.
All of this has happened before, and it shall all happen again if we are not careful.