To understand why a pre-workout is a delusion, you need to know how our digestive system works.
Our digestive system takes one to two days to digest the food, from input to output. The food we eat goes into our our mouth to the stomach, here it takes about 2 to 3 hours to process and then passes the food to the small intestine. The small intestine is about 20 foots long, which is equal to the length of two storeys. The small intestine absorbs the nutritions from the food and the rest is passed to the large intestine. The large intestine absorbs the remained nutrients and water from the food. The food is then excreted.
So, if it takes this long to digest, how will we extract the energy from the pre-work out and be able to use it in the period of work? The answer is, our brain gives us an illusion of having power to our body. The energy we might be getting would be the energy, from the food we ate yesterday morning. The importance of pre-workout is just to create a sense of full of energy during the workout. It can be efficient to not take pre-workout, if we train our minds from the beginning, about the timings of our workouts.