I can explain. I've been reading all these threads that have been popping up lately, suggesting tanks not wear STR accessories, and it's been an enlightening experience.
1.) Wearing STR means you have less health. If you have more health, you are able to survive more damage. If DPS in your group decide to stand in every AOE while you're taking damage, the healer could completely forget about you if you have more health and go heal this 200DPS MNK that is vastly more important than the tank. Your DPS as a tank is completely unnecessary and by doing more damage, you somehow cause the entire rest of the party to lose their minds and do less DPS.
2.) Having less HP means less healer DPS! Healers, especially in their opener, will only heal you once you've reached a % of HP. Obviously these healers have also forgotten about HoTs and fairy regen, so you basically just take auto attacks until you've reached 5 or so HP, then the healers will finally turn off Cleric and top you up. But wait, doesn't the tank with more health require more healing, thus resulting in lower overall DPS due to the healer and the tank using the same amount of GCDs yet the tank would be doing less damage because he decided against STR accessories? Nahhhhhhh.
3.) Everything you could possibly do as a tank > anything DPS related. Determination? No. Crit? No. Skill Speed? No. Parry? Yes! Parry will decrease your overall damage taken by upwards of 30%! Obviously tanks should take Parry, right? It's a tank stat after all, just like VIT. Stack on as much VIT as you can possibly get. Bonus points? VIT. Accessories? VIT. Potion? VIT. Food? VIT and Parry of course! STR has no place in a spot where you could have more VIT. VIT, after all, is all that matters for tanks. The less it seems like my health moves, the more comfortable my healers will be, and the more we can wipe to enrage.