Why does the president use the threat of a veto?

Answer 1

Because Congress cannot override it. The Constitution provides that a President has ten days (Sundays excepted) in which to either sign or veto a bill. Otherwise, it becomes law without his signature "unless the adjournement of Congress prevent its return, in which case it shall not be a law". This is to prevent Congress from evading the Presidential veto by passing a bill and than immediately adjourning, so that the President could not return the bill with a veto message. Accordingly, in the last ten days of a Congressional session, a a President may kill a bill without needing to veto it, simply by leaving it unsigned unil Congress adjourns. This is a "pocket veto".

Answer 2

The president occasionally uses the threat of a veto to force Congress to amend a bill to include terms favored by the president or to remove terms opposed by the president. If the president exercises veto power, the bill might be delayed, or it might not be passed at all.

Answer 3

Sometimes, he can get Congress to make changes that he favors in proposed legislation by threatening to veto it., or perhaps, if its backers are fearful that they do not have the votes to override a veto, they may kill the bill without ever sending it to the President.