It just feels so good to counter a big removal spell from the opponent, or even a cheap removal spell in the early turns
The set designers wanted to give a whimsical, ephemeral identity to the planes elemental creatures, since they were going to receive typal support and needed something to tie their cards together across all five colors
A lot of the on-theme finishers (Meloku, Multani, Avenger of Zendikar, Rampaging Baloths, Primeval Titan) are at a high power level, which is great for convincing the power-max crowd to try it but awkward if you're trying to tone things down
In fact, I think with Force of Negation I hard-cast it about a third of the time, compared to Force of Will, which I hard-cast probably less than 10% of the time
Because it has a powerful ability that lets you ready cards again and can earn 4 Lore when it quests, its coveted by both players and collectors