Selecting "hard" finishes for a new build or renovation can be a daunting task. Using large samples to see how the undertones coordinate can make a big decision easier. "Hard" finishes can include tile, countertops, flooring and those other typically large-scale, hard-to-swap-out finishes.
One of the best ways to pull a design together, is to start with the finishes you have limited selections on (IE - your hard finishes), and select your paint colours to coordinate with those, since paint colours come in literally thousands of colours!
Holding a range of large samples up against your other options can help you narrow down what the undertones in your hard finishes will match with, or clash with, and pull together cohesive design.
For example, picking a bright white blueish-toned marble, you will most certainly see you'll need a brighter white to coordinate with. Holding up creamy whites that could be a potential cabinet colour, will show you how "off" the two colour families would look together. Try holding your samples in the direction they will be oriented in in the end as well; ie - cabinet colours, hold your paint chips vertically up against a horizontal quartz or marble piece for your countertops. The direction can alter the lighting/overall look a little bit as well.
Or, if you're repainting walls in your house, and leaving your baseboard and casing as is, comparing a large paint chip against them can help make decisions easier here as well. Compare in a few spots; near the floor at your baseboard level, and up at eye level as well around window trims to make coordination easier.
Large paint samples can make the design selection process much easier overall. I hope they help to install confidence in your selection process and truly help to put together a cohesive package for your home.