One day when Steve Walker was strolling past the White House, he noticed that a meeting had apparently just broken up. Several prominent people were emerging, among them Sen. Henry M. Jackson (D-Wash.).

Steve says that Scoop Jackson walked over to his car, which was parked on the White House driveway and "then he did something that astounded me. He took out his keys and unlocked his car! On the White House grounds!" After all, could there be a safer place to park an unlocked car?

Perhaps not. But Scoop's habit of locking his car doesn't astound me. I'd have done the same thing out of forced of habit.

The only time I leave my car unlocked is when I turn it over to somebody who will assume responsibility for it - such as an attendant at a car wash, or at a repair or parking facility. With me that's not just a firm rule, it's a habit. And I think a good habit.

Over the years, I have seen too many news reports of unpleasant incidents that flowed directly from the fact that cars were left unlocked - even for "just a minute."

Neighborhood children get into unlocked cars and do damage to themselves or to the contents of the car. Many a man has left his unlocked car in his own driveway and emerged to find it smashed up because a child who was pretending to drive had released the handbrake and sent the vehicle rolling down an incline.

Thousands of teen-agers have taken their first step toward criminal careers by yielding to the irresistible lure of an unlocked car. Why subject an immature kid to that kind of temptation?

In the vast parking lots that surround shopping centers and supermarkets, unsavory characters sometimes enter unlocked cars and hide themselves in the space behind the driver's seat to await the return of an unsuspecting victim. Sometimes they release the hood latch inside the car so that they can steal the battery. While they're at it, they have a chance to get into the glove compartment.

Who needs all these avoidable headaches? It takes only a moment to lock or unlock a car, and you can eliminate all these needless risks by getting into Scoop Jackson's habit of locking up every time you park. Even when they let you park inside the fence at the White House?

Incidentally, if you talk to the insurance people they'll give you one other good reason of Americans don't lock their cars when they park costs all of us untold millions in higher premiums because an unlocked car is ever so much easier to steal.