1) If your business is not on google, it does not exist. 2) Up to 90% people search their required services on google first, so play wise.
Better User Experience
If user finds your website on first page of google means chances are he will enjoy experience being on your website.
Organic Traffic
This is FREE marketing only smart use of keywords on your website and activities you do outside.
More Business Leads
More search for your keyword will bring you more users from search engines, when users land on your website chances are high to convert that into lead.