You uh... haven't seen how they were treated in 1.0, huh?
A boy in 1.0 didn't believe in the elementals and to prove it, dug an axe into a tree and set it on fire. The elemental, thoroughly pissed at having its tree attacked, petrified the boy. He was
lucky to have the immediate intervention of two seedseers, including E-Sumi Yan, to beg the elementals' forgiveness.
When there
isn't a seedseer around to placate the elementals, well... people start getting
disintegrated left and right.
Their anger at the destructive use of aether that tipped the elemental balance is also believed to have been the straw that broke the camel's back regarding the Sixth Umbral Calamity, triggering a planetary flood of Biblical proportions. The Twelveswood is the elementals' home first and foremost. They're the cranky landlords who allow Gridania to exist in exchange for protection and careful use of resources. Pissing them off is just asking to get dusted.
The reason why you don't see the elementals as much in 2.0 onward is because they were gravely weakened by the Seventh Umbral Calamity that torched much of the Twelveswood. As such, they're no longer able to directly punish tresspassers and transgressors for their woodsin, instead stirring the local wildlife and awakening treants to viciously attack any human-shaped thing near the point of injury. So even then, their presence is felt, and they have enough power to do great things like pull someone out of the lifestream or nullify an otherwise fatal toxin when asked and given proper compensation.