Lawn edges have more crabgrass. Weaker grass = More Crabgrass
Weeds and crabgrass are always more of a problem where the lawn is weaker. Lawn edges can have issues that can cause the grass to be weaker than the lawn that is in the middle of the yard. Weaker lawns means more crabgrass.
String Trimmers (whipper snipper, weed whacker) These are often commonly used to trim the lawn at the edges. And scalping the lawn here is also common. When the grass is cut too short, we call that scalping. When the lawn is too short, there is less leaf blades to shade the ground and reduce weeds and crabgrass.
Scalping with a Lawn Mower – the lawn mower can also scalp the lawn along the edges of the lawn. When the wheels of the mower go down into the flower bed or onto a walk that is much lower than the lawn, the mower blade will scalp the lawn.
Paving Next to the Lawn – Concrete, asphalt, and other hard surfaces can make life hard for lawns. These surface absorb the heat from the sun and then transfer that heat to the soil nearby. Warmer soils can stress the roots of the lawn.Crabgrass prefers warms soil and will outperform lawn grasses along paved edges.
Also, when driveways or walks are installed, there is usually gravel under the concrete or asphalt. This gravel can sometimes end up under the lawn next to the paving. This can also negatively affect the lawn along the edges by creating poor conditions and warmer soil.
more links to crabgrass
Weed Grasses - Crabgrass in the Summer ...
What can I do with crabgrass in my lawn? ...
Is My Crabgrass Up Already in April? Or is it Quackgrass? ...