It's also an issue the majority party is such because they gained favor in constituencies that are prone to political swing and that it might not be in the interest of members of the majority party to vote with their party because their future in this job is contingent on a constituency that may not be reliable for either party and will go back to the opposition's party if you vote in a way that is not popular with the constituents in a majority. In addition, the rules of both houses often require more than simple majorities for non-budgetary laws.
For these reasons, it is easier to say "No" on a bill than it is to say "Yes", because the yes will require at least 51% (218 in the House, 51 in the Senate) to aggree to every single provision in the law, while a "No" requires 51% or more to have a problem with the law (consider that the minority will oppose because it goes to far, but the majority can contain a moderate who knows their constituency will also agree the law goes to far, but can contain a hardliner who believes the bill doesn't go far enough!). To give a great example, Abraham Lincoln's legislative agenda was equally frustrated by the Radical Republicans who wanted Lincoln to take a tougher stance on abolishing slavery as much as opposition from Democrats who counted Lincoln as a Radicle Republican because he was a Republican (And keep in mind, there were still states in the Union that permitted slavery at the time.).
Lincoln's successor, Andrew Jackson, was considered so soft on handling the reconstruction era south, that the Radical Republicans nearly voted to convict him on Impeachment (the deciding vote sparing Jackson was cast by a Democrat).
The U.S. political parties exercise very little ability to actually enforce their members in office to vote party line on an issue, and sometimes a bill never makes it to committee before it's clear that the votes simply are not there. And given how the balance of power can shift every two years, it's not worth it even if the party that proposed it is in control of the legislature.
To top it off, the some bills might not make it out because while there are enough votes to pass the measure, there are not enough votes to override the President's veto.