When Samsung first introduced the Note Edge in 2014, many criticized its curved display as gimmick. Samsung marketed the "revolutionary" curved edge display as a "groundbreaking way to deliver information". At the time, the tiny sliver of display could only convey so much and it wasn't flexible by any means. But, as Samsung has improved their technology, so has the usefulness of the edge display. Although the edge display is still for the most part viewed as a gimmick, with improvements to the interactions and what can be displayed, Samsung has elevated the edge display into something a bit more useful.
Instead of relying on stacking information solely on the curved portion of the display, Samsung expanded its efforts with the S6 edge to offer "edge panels". For the most part, this offered a new way to access apps, by tucking them in a special panel that could be swiped in from the left or right hand side of the display. Although customizability was not that high, it did offer the ability to access five custom apps and contacts.
With the S7 edge, Samsung takes things a step further by expanding the edge panel to accommodate two rows of apps and a plethora of new edge panels. While not everyone will utilize the panels, there are quite a lot of options when it comes to displaying information. If the default panels (12) aren't enough, you can go online and download more, with some being free and others requiring a $1.50 to purchase.
While I wouldn't say that the edge panels are completely necessary, Samsung has done a good job of making them more functional with each iteration. Although the S7 edge's curved display and edge panels might still be seen as a bit of a gimmick, they still offer something more to the experience - although how much more will be entirely dependent on your utilization.