Deckie makes it easy to view any of your decks (or search for a card) without leaving the current page you're on.
Have you ever seen a deck screenshot online and wanted to compare it to one of yours? If your store your decks on a website you have to open another tab, navigate to the site and resize your windows to get a side by side look. With Deckie it's just one click.
Maybe you're not familiar with a card and would like to know more about it? No more need to do three or four steps when you can get the same information from Deckie.