Why was the Robinson couple happy to find the cotton in the classic The Swiss Family Robinson?

The Robinson's were thrilled to have the cotton. They used it to make beds and cloth.

Fritz galloped forward, and returned, bringing me a branch loaded with this beautiful white down, which, to my great joy, I recognized to be cotton. It was a discovery of inestimable value to us, and my wife began immediately to enumerate all the advantages we should derive from it, when I should have constructed for her the machines for spinning and weaving the cotton. We soon gathered as much as filled three bags, intending afterwards to collect the seeds of this marvellous plant, to sow in the neighbourhood of Tent House.