Why does Hester from The Scarlet Letter take such care in crafting her clothes and letter?

Hester meticulously designs and crafts her sewing for several reasons.

1. Her intricate embroidery of her letter demonstrates her attitude about her "sin." In a way, it is a sort of rebellion against all the people of Boston who are just as guilty of sin as Hester, yet who have no outward symbol for their sin.  This reason for the novel's embellishment fits the Hester at the beginning of the novel.  Additionally, as Hester creates her own place in the town, she chooses to wear the letter even after she is not required to do so.  The letter's beautiful appearance does not mean that Hester is not sorry for her sin; rather, it shows that she has come to accept what she is known as.

2. After Hester gives birth to Pearl, receives her public punishment, and is privately spurned by her husband, she knows that she must make a living for her daughter.  She does so by sewing, and the letter along with her and Pearl's clothing are a sort of advertisement for Hester.  Like it or not, the people of Boston are after all hypocrites, and regardless of how they pretend to feel about Hester's "sin," they will not hesitate to take advantage of her skill with a needle.