AR sits on the balance sheet as a current asset because it is expected to turn into cash within a year, usually within the payment terms on the invoice. For a B2B service business, receivables are often the largest asset that is not cash, and how quickly they convert is the difference between a healthy cash position and a line of credit.
The two questions to ask about receivables are how much (the total open balance) and how old (the aging report). A growing total is fine if sales are growing; a growing share past 30 or 60 days is not.