Probably because you tailor the plants you grow outside by the amount of available sunlight. If you grow indoor plants that require more sun you can use supplemental lighting. But to do so outdoors doesn't make a whole lot of sense.
It can be dangerous and expensive! Not to mention interfering with your neighbors property. I would really ask you to think about rainfall, runoff, seepage, thunderstorms, electrocutions.
If you do not have enough light to grow a large fruited tomato that takes 80 days to mature and you need more sun, you trim a tree, you can cut down a tree to get more sun. Why on earth would you use supplemental lighting outside?
If cutting down trees or trimming trees is not an option, you grow a different type of tomato, either a cherry tomato or a Roma tomato.