Final answer:
The state's policy goal for taxing online purchases is to ensure competitive equality between online and physical retail stores and to bolster state revenue for public services.
Step-by-step explanation:
The policy goal behind taxing online purchases within a state's borders is to level the playing field between brick-and-mortar stores and online retailers. The government hopes to encourage fair competition by ensuring that online stores don't have a tax advantage over physical stores. By subjecting online purchases to sales tax like any other in-store purchase, there is an incentive for consumers to potentially shop locally rather than exclusively online, which may also support local businesses and the state's economy.
Furthermore, applying a sales tax to online transactions helps increase state revenue, which can be used to fund public services and programs. It also reflects the current economic environment where e-commerce has become a significant part of consumer habits, and thus states need to adapt their tax laws to capture this source of revenue efficiently.