Why should you have your parking lot swept?
Several reasons exist why you should have your parking lot or street swept; 
The first reason is to preserve the surface of the parking lot or street.  
Sand, rocks, and gravel all have an abrasive effect on the surface and can contribute to wearing. Causing it to deteriorate quickly.
A second reason is the aesthetic value of your property.
  What impression do you want to send to your prospective customers?  First impressions are very important and a parking lot or street filled with garbage, dirt and other debris does not create a positive impression.