Just simply put, rng
When CT first came out no lies it had taken me around 80 runs just to get the Crimson hat, chest was around half those runs.
Ifrit's bow, same thing close to 80 or more runs (i ended up getting months after my Relic)
Atma had taken me approx 4 months to get all of them, while people who have started a month or so after me had gotten 2 atma weapons by then. And yes i have done way more fates, i got that 3,000 fate achievement a while back, lol
Drops in dungeons rarely do i win rolls which brings me to ST, more often then not i must go in there with people from fc that have all had their loot already or they all pass, because yeah i don't ever win. So yeah, hooray for me