There is no bhakti without myth, no love without bhakti. Human beings are myth-making creatures because there is no reality without myth. Where would your reality go if it had no myth to follow?
Radha and Krishna are eternal archetypes. There is not much point in historical references except to see how the concept of the sacred nature of human love has developed.
As our understanding of love as Truth develops, our giving sacred form to that Love symbolically becomes a necessity.
Symbols encapsulate entire constellation of ideas. The words "Radhe Shyam" contain both the myth and the reality of Love. So sing the names of the Divine Couple.
Radhe Shyam! Radhe Shyam! Radhe Shyam! Radhe Shyam!
If our symbols are not consciously sacred they become mundane. It is better to take a mundane symbol of love that approximates the purity of the Ideal and attribute sacred character to it than to be without any sense of the sacred whatsoever.
But better than that is to subsume all manifestations of love, to the degree that they are pure, into the overarching archetype of the Divine Couple. That way, the sadhana of love becomes possible, because it gives a point of connection between the Divine and the human.
Once the Divine Center in Radha and Krishna has been discovered experientially, however, all other partial symbols fade into insignificance, or simply become reference points for the sake of communication.
But for the sadhaka, there are so many of these "partial" manifestations that it becomes distraction. Abelard-Heloise, Cyrano-Roxane, Romeo-Juliet, Tristan-Isolde, Kama-Rati, and all the ancient mythical divine couples from Isis-Osiris to Lakshmi-Narayan, are mere ripples in the sea of Radha-Krishna.
What to speak of you, finite creature, and your lover!