To understand why, we have to understand the core conservative governing principle - aristocracy.
In 1760, the conservatives in North America were those who were loyal to the hereditary aristocracy of the British Crown. By the 1780s, as the Constitution was being written, the royalists had left the country for Canada or the UK and the remaining conservatives had shifted their advocacy of aristocracy from one based on genetics to one based on wealth.
The liberals who dominated the Founders and Framers of this nation, however, disagreed. They thought that if there should be any sort of an "aristoi" it should be based on merit, and change from generation to generation.
Jefferson and the liberal Founders like Madison, Franklin, Washington, and - particularly - Tom Paine, believed, on the other hand, that if the largest portion of the people were given the largest portion of the power of governance, then they would correct errors they themselves made, and correct them quickly because of the impact they'd have on themselves. In their support, they quoted Locke, Rousseau, and the experience of the Iroquois Confederacy. The liberals represented by Jefferson and Paine have, since the founding of this nation, argued for a meritocracy based on "the best and the brightest" rising up from among the people to enter public service.
Early on in the debate, the Adams side won most of the argument. The President would be elected not by the people, but by "wise elders" appointed by the states (the electoral college). The Senators would not be elected by the people, but appointed by the politicians of the states, with the overt and clear purpose of representing the interest of wealth and capital in those states. Only the House of Representatives was to be directly elected. (It wasn't until 1913, with the passage of the 17th Amendment target="_new">17th Amendment, that we began to directly elect US Senators - the result of the progressive movement that arose as
a backlash against the Gilded Age.)
"I agree with you that there is a natural aristocracy among men. The grounds of this are virtue and talents. .
"There is also an artificial aristocracy, founded on wealth and birth, without either virtue or talents..
"The natural aristocracy I consider as the most precious gift of nature, for the instruction, the trusts, and government of society: And indeed, it would have been inconsistent in creation to have formed man for the social state, and not to have provided virtue and wisdom enough to manage the concerns of the society.
"May we not even say, that that form of government is the best, which provides the most effectually for a pure selection of these natural aristoi into the offices of government?
"The artificial aristocracy [based on wealth] is a mischievous ingredient in government, and provision should be made to prevent its ascendancy.
"On the question, what is the best provision, you and I differ; but we differ as rational friends, using the free exercise of our own reason, and mutually indulging its errors.
"You think it best to put the [wealthy] pseudo-aristoi into a separate chamber of legislation [the US Senate], where they may be hindered from doing mischief by their coordinate branches, and where, also, they may be a protection to wealth against the agrarian and plundering enterprises of the majority of the people.
"I think that to give them power in order to prevent them from doing mischief, is arming them for it, and increasing instead of remedying the evil. For if the co-ordinate branches can arrest their action, so may they that of the co-ordinates. Mischief may be done negatively as well as positively. Of this, a cabal in the Senate of the United States has furnished many proofs.
"Nor do I believe them necessary to protect the wealthy; because enough of these will find their way into every branch of the legislation, to protect themselves. From fifteen to twenty legislatures of our own, in action for thirty years past, have proved that no fears of an equalization of property are to be apprehended from them.
"I think the best remedy is exactly that provided by all our constitutions, to leave to the citizens the free election and separation of the aristoi from the pseudo-aristoi, of the wheat from the chaff. In general they will elect the really good and wise. In some instances, wealth may corrupt, and birth blind them; but not in sufficient degree to endanger the society. .