Why does a major food producing country like Bangladesh import any food at all?

In the whole world, there is no country which is specialized in all the products. For this reason, being a major food producing country like Bangladesh imports any food at all. In some food cases, the production cost is higher than the importation cost and sometimes many cases importation cost is higher than the production cost. Because specialization factor is behind it.
Though Bangladesh is a major food producing country, it imports some commodities in which it isn’t specialized. It hasn’t the comparative advantage of these products and the production cost is higher than the importation cost.