The book “Toyota Supply Chain Management” by Iyer, Sheshadri & Vasher describes how Toyota in the US anticipated port strikes and piled up inventory of imported materials. They sailed smoothly through the crisis when it occurred. Their competition struggled with shortages in the strike period. Anybody would quickly agree that they have acted sensibly. There are plenty of other situations and business environments where stocking is essential and even profitable.
One is where seasons determine consumption like in the case of fertilizers for agriculture. Fertilizers are consumed in short windows of period in the annual crop cycle. In those windows millions of tons would be consumed. There is no technology to produce and distribute fertilizer economically in such a short period of time. Fertilizers can be produced economically round the clock in thousands of tons per day for stock. The demand for millions of tons in the short time can be met easily from stockpiles built across the market geography in months before. Thus the overall economics of making and stocking is optimized.
Also, an emergency situation causes heavy monetary losses when any important machine breaks down. It helps if one keeps stocks of spares. In such situations often the cost of spares is modest or insignificant compared to consequential loss to business. The cost of keeping spares is justified by saving breakdown losses.
Most sellers would not like to refuse service to a walk-in customer because of lack of stock. They know that net cash flow of margin is usually very much higher than the cost of keeping stocks. They would even willingly overstock for items in demand.
These are just commonplace examples. There are other temporary, situational and administrative benefits of keeping stocks. This is not to say that one should not be mindful of high inventory, but one should optimise it rationally.