Starch reduces the chance of wrinkling and can make ironing easier.
It also helps to keep a nice crisp crease in trousers or a shirt sleeve.
This icon was officially endorsed by the United Nations in mid 2019 and included in the GHS Sub-committee guidelines (Globally Harmonized System of classification and labelling of chemicals).
If you are going to store articles for a while, do not starch them first. Starch attracts bugs and can cause items to yellow over time.