ROCKVILLE CENTRE, N.Y.  The “Downtown” that Petula Clark evoked in her 1964 pop song of that name (where “you can forget all your troubles, forget all your cares”) never made much sense to anyone who worked or lived in an actual downtown. It was a song for people who did not.

So, blaring from the public address speakers to open a recent meeting here, Ms. Clark’s hit was probably the perfect score for a conference of suburban officials and planners promoting the idea that Creating Cool Downtowns, the conference title, was the future of the suburbs of New York.

“Young people are moving to Manhattan. They are moving to Brooklyn,” said Thomas R. Suozzi, the Nassau County executive and organizer of the conference, which was held on Friday in the parish center of St. Agnes Cathedral.

“Why aren’t they moving here?” he asked.

Why young people flee the suburbs was the underlying question of the day. But there has never been much mystery about it: There is nowhere to live; not enough to do; and not enough young adults around to improvise the kind of neighborhood scene born every few years in the big city.