Because most Congressturds on both sides of the isle rarely read the actual bill they are voting on. The sponsors of the bill put out a memorandum in support of the bill that summarizes the proposed legislation, what it amends, what it does, why Congress should pass it, and the fiscal implications. The various committees that review the bill also put out a summary memo in support of or in opposition to the bill. Very few people read the actual legislation, however.
Is this the ONLY job where you can make a ton of money by not doing what you are supposed to do, and if you don't like what you make, you can simply vote yourself a pay hike?
Every congressman and senator should be required to verbally read aloud every bill up for a vote at least 5 times before any vote comes up.