Question

Why is state government enter into formal agreements with each other

Answer 1

because the state list is totally in the hand of state.... thats why they need to do agreement

Answer 2

Answer:

Treaties, Agreements, and consultations are generally gone through to combat or deal with a mutual problem or challenge.

Alliances are formal agreements between two or more nations. In national defense, they're promises that each nation will support the other, particularly during war.
Treaties are the documents that seal the deal on alliances, so sometimes you might hear the term "treaty ally." Things like international boundaries, trade rules, human rights and even postal arrangements can also be set by treaties.
Partnerships are less formal than alliances. Often called "strategic partnerships," they help build relationships between nations or organizations like militaries. Like alliances, they benefit the members of the partnership, but they can be short-term and don't involve a treaty.