The Northern European folk regarded the supernatural beings commonly grouped together as fairies/elves/etc. as dangerous rather than evil. There were attempts on the part of the Church and the literate class to place these entities in the realm of evil, beginning with Beowulf and other early documents. This was a natural conclusion for the Church because according to its dogma, there were no unaffiliated parties in the struggle between God and Satan.

Despite these efforts, the folk tended not to see these entities as evil, but they feared them in a profound way: while faerie could reward people from time to time, it was a fickle realm and treading there was a dangerous prospect that turned out bad in the majority of cases.

During the Victorian period, there was a literary appropriation of faerie that transformed fairies, diminishing them in stature, power, and danger. This was not a matter of folk belief in its original, pre-modern/ preindustrial/pre-urban setting. Because various publications - and then films etc. - were so effective in communicating this newer adaptation of faerie, the new modern/post-modern folk of the literate world adopted this new definition. That is the process that you are observing with your question (setting aside the question of "evil" as opposed to simply "dangerous").

I hope that helps; feel free to ask questions.