It's an excellent question, and I'm reminded that the way in which you have practiced might have brought you here. These are the types of deep curiosities that can arise from an enquiring mind intent on seeking a deeper truth to all of this. I used to ask the same question when I was a child and then again many years later when I began practicing Buddhism. Incidentally, I was recently walking on the beach with my own child who suddenly asked the same question. I thought to myself, "you wise little sod!" Children in general have these types of deep curiosities because they have not yet succumbed to the heaviness of the world's neurosis. That's why I started with the way in which you have practiced might have brought you here because practice dissolves those neurotic tendencies and often leaves us with deeper questions.
There's good and bad news. The bad news is that your question cannot be answered. The good news is that the energy from your curiosity can be used skilfully. Let me explain...
The very fact that you are enquiring in this way is the beginning of the first discoveries of emptiness and follows the premise of MN121, The Shorter Discourse on Emptiness. At the time I wasn't aware of this teaching so, quite of my own accord here's what I did with that energy (my efforts were initially cumbersome to say the least but later became more refined due to studying MN121...)
In perception, I began removing things from my environment, coarse things like people and furniture. This left empty rooms if I was indoors and empty towns and streets if I was outside. Wanting to further enquire, I began removing bigger objects: buildings, roadways, trees, until there was only a vast landscape with its contours. Then I removed the earth, the stars, galaxies until everything appeared empty.
What this leaves you with is a subtle perception called nothingness. It is not actually nothing because there is someone there creating the concept of nothingness which is contingent on what was previously known about the presence of objects. This is consciousness, or more precisely consciousness regarding ideas and concepts: the concept of you perceiving the concept of nothing. The space/time consciousness becomes apparent here or the idea that space and time are just that: another idea. If you wanted to you could then work on removing the idea of nothingness with which things then become neither perception nor non-perception. Nothingness and neither perception nor non-perception are the two most intriguing of the four arupa ayatanas. They are not necessarily connected with the four jhanas meaning you can jump straight into cultivating the arupa ayatanas regardless.
It's around the region of the last two where reality starts to light up. It illuminates itself since it is not so much suppressed by the samsaric consciousness. As far I understand, this luminosity is another perception but a very significant one. That's about as far as I can go. I have no understanding beyond this point.
Just to summarize: your enquiry is founded and relevant, but the direction is not. There are no answers about why there is form and directing your attention there will only lead to frustration as ruben2020 mentioned in his answer.
However, as I've pointed out, one can direct this enquiry in a more skilful manner. MN121 does an exponentially better job than myself at doing this.