If your sales reps are aware that you can monitor their activities throughout the day by knowing their location, they will be much more likely to take responsibility for their work and give their best effort.
The more data you have available about your sales reps activities, the easier it will be to analyze their day to day work and make improvements. For example, you can figure out how often each sales rep stops for appointments, how long those visits usually take, and what route they are choosing. Using this information, sales managers can find and correct any inefficiency and improve performance by tweaking routes to perfection.
If your company is involved in door to door sales and or your reps spend time finding customers by speaking with them directly, then keeping accurate measurements of the correlations between field activity and sales results is very important. This area of sales tends to be quite expensive, all things considered, so keeping detailed and correct data may save you a lot of time and money.
When you are able to track sales reps, you can know for sure whether or not they are making their assigned stops and spending the most time in the right areas of the market.