SMS & Email used to be THE medium for sales. But WhatsApp is the new de-facto medium for customer communication.
WA is personal, people view WA contacts as friends so when sales is done well by only offering promotions during conversations as supposed to random broadcasts at 1AM, people respond better and thus generate effective leads.
There is huge opportunity to uncover customer sentiments & preferences to provide information that you are previously oblivious to. Examples: customer habits, winning products, peak hours, etc.