…cause of the lower ppi. And anything above, i.e. iPhone 6 plus is @3x since it’s density is 401ppi. For example, your icon size is 50x50px for iPhone 5/5s or even iPhone 6 art-board then your @1x size will be 25x25px and @3x size will be 75x75px.
It’s human nature to go to extremes. But extremes are rarely where progress is actually made. Getting better, honing a skill, or losing weight (in this case), comes with consistency and repetitive effort.