Have you watched a home being built? They scrape off all the topsoil and stock pile it. Then they dig out a basement and spread that soil around the yard. They drive heavy equipment all around the yard (and bury rocks and debris while they’re at it). When the house is done, they bulldoze it smooth and cover it with a little of that topsoil that they carted away. There are two problems with that. First, the processed topsoil has pretty much lost all of the biology that was giving it any structure and would provide plants with the oxygen they need to grow, its not great stuff. Second, the layer between the compacted subsoil (which roots will have a difficult time growing into) and the topsoil is a hardpan that roots and water have difficulty penetrating.
There are a few things, first of all you can introduce good biology that will help loosen and improve the soil. Compost is the best way to do this, but compost tea can also help. Secondly, you can help the grass by core aerating at least every fall. Using a liquid aeration in the spring and summer will also help to loosen the soil and encourage grass and roots to go deeper. Using soil Improvement services is an excellent way to create a healthy beautiful lawn.