You've invested precious resources to acquire your customers, and likely had to overcome a bit of initial distrust when they first bought from your company. If you keep delivering them solid value through related offers, and keep them satisfied through good customer service, many will be glad to buy from you again and again. Diversity reduces marketing and fulfillment costs. Per-item marketing expenses are reduced as each new product or service is added to your line, because each shares the marketing costs with all the others. Processing an order for multiple items involves nearly the same amount of labor costs as a single-item order.
Diversity reduces business risk.
You won't be totally dependent on a single income stream. All too often, entrepreneurs that recognize the value of diversity tend to promote a disconnected mixture of totally unrelated goods. However, the real benefits of diversity come from expanding your line of offers around a common theme. Rapidly I always recommend that you market at least one of your own core products or services that that you have exclusive control over. However, acquiring or developing your own products usually take time.