You get higher yields. Instead of guessing what your plants need, as you do in soil, you start by growing your plants in an inert (i.e. has no nutritional content) media such as Grodan Rockwool or Clay Pebbles and feed your plants the very best nutrients (i.e. hydroponic plant food) that you can buy. This way you know that your plants are getting exactly what they want when they want it.

You can grow more garden and plants in a given area. Because your plants are not competing for nutrients you can grow more plants in the same space as compared to soil.

Your plants tend to grow faster and therefore you tend to get more yield as a result. They are also healthier making them more resistant to pests and diseases.

You get less waste. It is much quicker, cleaner and easier to clean up after you have finished growing hydroponically than from a grow room with soil in it. There is also a lot less to throw a way. Soil is bulky and dirty whereas in hydroponics your growing media tends to be fairly minimal.