It's honestly because the linear no-RNG-allowed gear progression in this game just flat-out doesn't lend itself to content like this. We can already look at the reward for it and decide if it's crap or not. There's no "chance" of getting some astronomically awesome game-changing drop off of doing this content (the mount is there but it's hardly game-changing, IMO), the rewards are right there and in-your-face, no alterations possible. That basically leaves zero element of excitement amidst the doldrums of mob grind, which was the entire IMPETUS for FFXI gameplay.
Also worth noting that the combat in this game makes mob grinding, frankly, one of the most dull contents you could possibly aim to do. There's no flashy combo elements like in BNS or BDO to hold your attention, but there's no slow deliberation of meaningful CC choices, debuffs, or resource management like in older games (XI, EQ) either. Outside of raiding (maybe dungeons, but idk man), the combat in this game just...isn't fun. It's plodding and basically devoid of reaction or choice. So mob grinding really exacerbates that because you can't make up for those combat shortcomings with say, interesting mechanics like you can in a raid. Like your drunk uncle at a bachelor party, it's all just left...hangin' out.
