Why was salutary neglect important?

The British established colonies in North America so that the British would benefit from having these colonies. The British got raw materials from the colonies and then sold the finished products made in the British factories to the colonies. This gave the British a guaranteed market for their products. To ensure that the British would benefit from the colonial trade, they established laws known as the Navigation Acts. These laws required the colonists to buy certain products only from Great Britain. The colonists were also required to use British ships when trading. However, the British often did not enforce these laws. This was known as salutary neglect.
The colonists became used to the lack of enforcement of the Navigation Acts. They illegally smuggled products from other countries and used the ships of other countries. When the colonies became more expensive to operate, the British began to crack down on smuggling. This angered the colonists. After the French and Indian War ended, the British began to pass laws that angered the colonists. Some of these laws dealt with trying to control the smuggling that was occurring. Other laws controlled where the colonists could go or created new taxes. The Proclamation of 1763 and the Stamp Act were examples of these laws. These events helped lead to the start of the Revolutionary War.
https://www.history.com/topics/american-revolution/stamp-act

https://www.ushistory.org/us/9a.asp

Salutary neglect, which was the British policy towards the American colonists in the early to mid-1700's.  It was a system of loose imperial control over the colonies and a lax enforcement of trade laws.  The Navigation Acts made it impossible for colonists to trade with nations other than England.  This led to smuggling of goods from the colonies.  England turned a blind eye towards the abuses of the colonists during this period.  The result of the period of salutary neglect was that the colonists learned to govern themselves and manage their own economies.  An elite class emerged in the colonies that benefited from the autonomy.  After England's prolonged war with France that included the French and Indian War in North America, the crown was desperate for increased revenues.  They looked to the colonies for this bump in revenue.  When England decided to enforce the tax and trade laws that were already on the books, the American colonists ultimately rebelled and the American Revolution was born.
https://www.britannica.com/topic/salutary-neglect