Fae don't exist as matter they reside in matter, they live in the spaces in between. Whilst all else spins and moves to create the reassuring semblance of solidity, Fae exist as the essence of stillness which by being truly still creates the mirage of movement.
When a human cannot generate, from will, the required intensity to bridge the gap between it's individuality and it's collective connection to that which extends it life, then Fae condenses as an electrical bridge, thereby allowing conductivity and reconnection. Commonly referred to as being touched, it allows an enhanced awareness and flow that constitutes healing and realignment. Also because it is an enhancement not a right, there is by necessity a requirement upon the human for their appearance.This creates a new set of problems in that the behaviour of the enhanced human changes as it comes to terms with the new perceptions and inherent values that now pervade it's conciousness. More often than not the presence of these enhancements leads to the disenfranchisement and exclusion of the individual from the material acceptance of the brain collective commonly known as society because these enhanced people now exhibit an ability and knowledge that makes them disruptive and or dangerous to the established order. (Think witch-hunt)
If the human, by choice, consistently reaches beyond it's personal power capabilities then the bridge becomes a permanent line connection and the Fae acquires a form recognisable to the human involved. This form is constructed from the patterns of recognition already existent in the human and the Fae will from that time until it's release manifest in this form. This form then attaches to that Fae in a similar way that a human would acquire a garment and if that Fae is again called into service it will wear it's garments or forms until such time as the new contract manifests it's own recognisable form.
In other words, because people expect to see Fae as the Victorians did, and because Fae expect to be seen as the last humans they dealt with saw them - that is how Fae are perceived. Note perceived not seen. It is only through an extended exchange that the Fae can offer a more contemporary form specifically tailored to the human making petition for enhancement.
If any of this makes any sense to you try and adopt it as a filter and go and look at the history of Fairy Art from it's heyday in the Victorian era right through to it's manifestation now in Science Fiction/ Fantasy Art.