Well, gathering has always been full of RNG, particularly since they added timed nodes for star gathering. Same for crafting, has been more and more about RNG too since they added star-crafts in realm reborn.
That's the easy answer, it's like going to a casino and making people addicted.
But it is also quite a japanese one in fact. They love RNG in Japan. When you want to buy a poster of your favourite manga in Japan, you get these RNG rolls. Go on, buy 8 and hope to get the one you wanted. You eventually will, after spending 20x the amount you'd have put into this beforehand. It's the same here, you'll eventually fetch your items, having spend 20x the time you initially planned.
But somehow I can't seem to be able to stop. Damn I'm addicted :(
It's the only way to get items you want so you just have to do it or stop altogether... but stopping would mean not being able to do what you want in the game so we can't stop....
You're right, it's not fun, but it's the only way now....
