The large majority of bills introduced in a legislature never receive a vote. The mechanisms that stop them are procedural rather than dramatic, and they operate before any public debate.
Referral sets the first obstacle
An introduced bill is assigned to one or more committees based on subject matter, and that assignment determines who controls its fate.
Multiple referral is common for bills touching several areas, and each additional committee is an additional point at which the measure can stop moving.
Sponsors sometimes draft language specifically to influence referral, since a bill framed as a tax matter and one framed as a health matter go to different places.
The chair controls the calendar
Committee chairs decide which bills receive hearings and which are scheduled for a vote, and declining to schedule requires no formal action or public explanation.
That power is the single most common reason legislation stalls, and it operates quietly because nothing appears on the record when nothing happens.
Procedures exist for forcing a bill out of committee, but they demand a large coalition and are used rarely, which is why they make news when attempted.
Hearings serve several purposes at once
A hearing gathers testimony, but it also builds a record, generates coverage and lets members gauge whether support exists before anyone has to vote.
Bills sometimes receive a hearing with no intention of further action, giving sponsors visibility while leaving the measure where it is.
Markup is the stage where a bill is actually amended and voted on in committee, and reaching markup is a far better signal of prospects than a hearing.
Floor time is genuinely scarce
Even a bill reported favorably must compete for chamber time against budget measures, nominations and priorities set by leadership.
Legislative sessions have fixed lengths, and bills that do not clear both chambers before a session ends generally must be reintroduced from the beginning.
This deadline pressure is why unrelated measures are frequently attached to larger vehicles that are certain to move, which is a routine feature rather than an anomaly.
Stalling is often the intended outcome
Introducing a bill has value even when passage is unlikely, allowing legislators to register a position and give organized constituencies something concrete to support.
Opponents in turn prefer inaction to a recorded vote, since a bill that never moves produces no roll call anyone must explain.
Rules differ substantially between the federal Congress and individual state legislatures, so the specific procedures depend on the chamber a bill was introduced in.