This is one of the best non-chemical treatments for a healthy lawn also considered as one of the most important things you can done to your lawn each season, this mechanical core removal process allows fertilizer, oxygen and water to penetrate deep into the roots where healthy grass germinates, it also prevent compaction and diseases. It is very difficult for water and nutrients to penetrate compact soil, if the majority of the water and nutrients material is located close to the surface of the ground, the roots of your grass will also grow close to the surface.
This makes the roots susceptible to damage from heat stress, foot traffic, freezes and wind chill. The deeper and more extensive the grass root systems are, the thicker, greener and more healthy your lawn will be. Spike aeration does NOT accomplish this nearly as well, spike aerators simply poke holes in the lawn but do NOT remove the cores. Strong healthy roots also help your grass to naturally fight off diseases such as Dollar Spot Fungus, Bipolaris Disease, Brown Patch, etc. Dollar Spot and Bipolaris Disease are most evident, in lawns that are stressed and have weak roots, and is often first seen around the edges of the lawn by sidewalks and driveways, this is due to the increased soil temperatures from the concrete and asphalt which compact the soil and damage roots.
Even if your lawn is lush, thick and green, you should still core aerate it every season. Aeration is more useful as a preventative measure than a corrective one.