Not entirely. It starts as that, yes, because the first thing you do when attempting to break into a house is check the front door. There are obviously levels beyond this.
> is like asking why gun designers don't find new jobs as infantry.
But it's not entirely like that. There's plenty of firms that hire out security specialists to do code reviews for internal applications. At that point, it's like a gun designing consulting for manufacturing firmson ways to make their products more resistant to small arms. The job won't be the same, but there will be commonalities and the prior experience will transfer over usefully.