Because that pesky, old, outdated constitution made it difficult to get treaties passed, requiring 67 votes, amendments, debate and congressional input throughout the process.
So, our congressional non-leaders, decided to give all their equal-branch powers away with a novel idea....Fast Track authority.
They first had to redefine trade deals as not the same as a treaty (even though both are agreements between nations).
Then, they knew if details were released early, opponents could gin up opposition, so they decided to take congress out of most of the process.
This version of the TPA includes giving even more powers to the executive branch than previous versions. In the hands of Obama, that is a disaster in the making.
Throughout Obama's term, it seems Congress has kept relinquishing power to the executive. It has happened before, but not to this extent. so our elected leaders decided to shortcut the constitution
I note they say this has been in the works since 2009, so I ask who has been in charge since then? Any fool, listening Cruz et al, who believes anything this guy wants to do is in the best interests of this nation, as it now stands while tottering on its foundations, is a bigger fool then can have his motivations to do so based on trade only policies. This agreement, thanks to Wiki btw, goes way beyond lowering tariff barriers and the like, it is a way to make trade our national religion kind of like how Islam is above any government or nation. It must be defeated. Those who support it must be removed, peacefully, but if not and may come to something more chaotic. When NAFTA was in the works, Perot was pillared over his giant sucking sound comment about the sound being the US sucked into Mexico. I guess we have not learned enough of a lesson. Today we want to do the same things on steroids while led by a despot who is a megalomaniac.