Any business will have to invest in materials if they want to earn market share, and not all of them will have to do with producing products. The businesses offering services only will have outlay for marketing materials, office expenses such as computers to find and track clients, and they might even provide items such as employee uniforms to be worn while service is being provided. All of these items do add to the expense side of the balance sheet, so cutting them can potentially make a business profitable over time.
Materials for businesses creating products for their customers are often seen as a place where expenses can be trimmed. A smaller or newer business providing raw materials might give better price discounts, or an established business could be looking for more customers. A deep discount might be possible from that source. Even companies using inexpensive materials can find their expenses adding up as they break into the market, so seeking discounts can help them turn their business into a profit center.