Why these and not others?
It is simply because they are, overall, amongst the most important Deities in the Creational thing. Each one has its own dimension and origin in Creation. All three are of the highest order in the scheme of things, especially in and towards the existence of the human being. Describing each one would take volumes of work, so this explanation approaches the question as a primary motivation to practise within a developing life along a Creational way. We exist in a three-dimensional universe and likewise every religion as far back in time as you can go, has also had to rely on a triad of deities that have figure headed their practices and ceremony e.g. Father, Son and Holy Ghost, Isis, Osiris and Horus etc. What it boils down to is that they are the covenant and power source by which most make religion and ceremony. The assuredness of Light, Life and Love are obvious and in comparison, even the natural laws of the Universe are dependent on a similar triadic condition to exist (that for something to happen there must be three influences acting upon the same situation at the same time, in the same space).
Without the presence or event of Light there would be no Creation. In human terms the Light is always to the higher processes, such as the core/soul, spirit, mental and inner life abilities that learn and contain it. Light has three main ingredients, thermal, nutrimental and electrical and because light is visible to the human eye it has a manifest illumination on all things.
Without Life, any organic existence would not have emerged from the ground to be what it is today. Life requires process to maintain itself, giving what lives the promise of tomorrow in that which lives might or could evolve into something greater. One example of this is the caterpillar, which becomes a chrysalis and then evolves into a butterfly. Humans are born complete but undeveloped and there are no books of instructions as to how to live on, other than what instinctive and motherly help they are given.
Without love, there would be no naturalisations or affinities to things or family of any species, including the human race. There would be no feelings, empathy or such processes as natural clairvoyance that would have a place in the recognition and association of those of kind. It is upon each person and their own works within their own life to refine these three qualities that are foundational to their existence as they know it.
Here now is the first of three momentary views of light, life and love: LIGHT.
Light always begins in the higher (its source) and then is propelled or enters into a surrounding darkness that allows it uninterrupted passage. It (the light) holds within itself a magnitude of wonderment and an aura that filters like an essence or passion even unto our innermost soul or core. Light is the simplest and finest form of life but always the higher in its outcome e.g. light itself has no rules other than just to exist as itself regardless of what it manages to illuminate or reflect.
It touches us and makes us known, seen as things are found, regardless of level or rank, or even sometimes the unseen (that which also lives alongside us but does not have the whole physicality to be seen). If it touches you then it carries you to somewhere else telling its destination who or what you are. Time and distance are no rule for it; it is itself, an instant or moment that lives on forever, serving the Creational existence and experience.