This is important mostly for larger jobs. Clearly a two man operation is going to build a home much slower than a 15 man crew. This is also a good indication of the overall size of the Additions and Remodels company, if that's an area of concern for you. The reason you may want to ask about the fleet is that fleet size is a good indicator of the mobility of the company. Mobility may not sound important, but it's hard for the Newport contractors to get to job sites if they lack appropriate vehicles.
Always ask for references, and always check them. Keep in mind though that the only references you'll get are people who the contractor is certain will give him a good review. You'd also be well advised to check online review sources in Newport as well, which will give you a broader view of customer satisfaction for a given company.