Calico fabric has a number of uses.
Clothing Samples
Calico is inexpensive and thus is a good choice for sample clothing designs for blouses, dresses and gowns. It allows designers to show off their creations or try to sell them without having to buy the expensive material that such an outfit might require in order.
Sturdy Bags
Calico is coarse and holds up well, good for items that should be cheap, sturdy and don't need to be pretty, such as a fabric bag.
Crafts and Quilts
Calico is used for aprons and patchwork quilts, and is often used in craft projects. Calico typically is available in solids, which is good for quilts. Even in cases where the quilt calls for some type of print, you can still use the calico as a backdrop for the coordinating print. However, calico is a tough fabric to use a needle on, so you may run into challenges using it for quilting.
Curtains
You can use calico to make curtains, The fabric comes in many colors and you can buy lots of it inexpensively. The fabric also doesn't need much ironing, which reduces how much work you have to put into maintaining your curtains.
Pillowcases and Duvets
Calico is a good material for pillowcases. You can find a solid color that matches your printed sheets, and the fabric is durable and soft. You can also stitch calico together and fill it with down feathers to create a duvet. The low expense of the fabric makes this easy to do without going over any budget you have.