Why does the concentration of DNA drop so much after each recovery?

In the PCR solution just after the reaction is not only your DNA, there are many impurities, such as the remaining primers, templates, enzymes, etc., gel recovery is the process of recovering the DNA of interest from the gel after electrophoresis, in the experimental process can be specifically adsorbed DNA by the corresponding material, remove the impurities in it to achieve the purpose of nucleic acid purification. In the experimental process, the removal of some impurities will naturally reduce the concentration of the solution, and electrophoresis will also cause the loss of some DNA, so the final concentration of the solution will be lower than before. However, the treatment of some details during the experiment can also increase the concentration of DNA to a certain extent, such as cutting the gel into small pieces to ensure that the gel can be fully dissolved in the water bath, and the use of fresh electrophoresis buffer can make the recovery effect better.