Starch and sizing additives can increase the firmness of fabrics, particularly on dress shirts. These additives can protect and harm shirts at the same time.
Shirts undergo two types of abrasions. Flat abrasion occurs when the shirt rubs against another surface. Flex abrasion refers to the stretching of fibers when the wearer bends an elbow or otherwise stretches the material.
Starch helps protect shirts by enabling them to withstand higher degrees of flat abrasion. However, since starch stiffens the fibers and makes them less flexible, it reduces the shirt’s ability to resist flex abrasion.
Starch’s primary function is to add body or stiffness to a fabric resulting in little flexibility. This lack of flexibility causes the material to snap under extreme pressure rather than stretch, decreasing the fabric’s tensile strength.
It all depends on how you want your shirts to look vs. how long you want them to last. The use of starches and sizings shortens the life expectancy of a shirt because these additives reduce the ability to bend, stretch, and straighten during use. Balancing out those negatives are the bonuses of having better whiteness retention, a crisper look, and increased stain resistance.