Do hardwood floors need to get glued to subfloor?
The best answer is one that will apply to your situation no matter what your region: Follow the manufacturer's installation instructions for that specific floor.  Should you have an installation related issue which side of right would you want to be?  The variables are your subfloor (wood or concrete), the wood flooring ((engineered or solid), and the regional characteristic circumstances associated with installation on, above, or below grade aka ground level.