musicmic, you have a conveniently selective memory, as pointed out by Sledge above:

In 1946, the bomb attack on the King David Hotel was ordered by Ben Gurion (Who went on to become an Israeli Prime Minister and Head of state). The attack was carried out by Stern Gang operatives who were under the direction of Menachem Begin (Who went on to become an Israeli Prime Minister)

In 1948, the murder of UN Mediator Count Folke Bernadotte by LEHI (Stern Gang). Yitzhak Shamir (Who went on to become an Israeli Prime Minister) was responsible for the planning and execution of this assassination.

Generally:
Alert Status, and change of alert status, as someone else has on this thread is specifically targeted at those responsible for the safety of the general population. They are the ones who have to put response measures in place and implement them, not the general public.

Should the general public be made aware of such changes? Yes of course they should. Anyone who has reservations about travelling can then either alter their travel arrangements or cancel them - the choice is theirs based on best information available at any given time. It also serves to increase the level of awareness of the general public to what is happening around them.

Announcing changes in alert status also deters the terrorists themselves, renders information gleaned through previous surveillance of targets useless, and sows doubts regarding possible security breaches within their own cells and organisation.