3 trains per hour for a total of 4 million trips per year? There's 35 million seconds in a year, making for a train every 7.8 seconds.

There's no question the train should be extended deeper into the city, but not into a tourist spot! They should extend the train down the Begin highway (either over it or in a tunnel underneath) so that it will reach heavily populated residential areas and business centers. There's no reason why someone who lives in Jerusalem can't work in Tel Aviv (and vice versa).