Because they are bringing evidence contrary to the mission of the court
<span>The delegates to the Constitutional Convention finally agreed the Three Fifths Compromise, that slaves should be counted at three fifths of their real number. The Three Fifths Compromise resolved the issue of counting slaves towards population in regards to representation in the House of Representatives.</span>
I think it has to do with the founding of Taxes cause mexico didn't like the land and offered it to the Americans.
I found this
The rendezvous served two purposes: celebration and business. For the trappers, the former was very important. For the traders, the latter was definitely most important. For their furs, the hired or company trappers received supplies for the following trapping season, perhaps some luxuries such as tobacco and alcohol.