All cameras and lenses have a limit of how close they can focus. This can be demonstrated by using a smartphone. How close can you get the camera to the end of your finger with the camera/phone getting it in focus ? A macro lens allows you to focus much closer, effectively making a camera into a microscope.
Getting closer to a subject allows you to get more detail out of smaller objects. Another advantage of macro is almost anything is interesting when you get closer which means you don't have to travel far to find interesting subjects, unlike landscapes where you need to allow time and research to capture anything meaningful.
I find it very therapeutic when walking in woodland looking for fungi (when i'm not being bitten) and can take my time while never knowing what I will find. Also it takes my mind off the weekly grind for short awhile.
The whole process of setting up and finding the composition is a rewarding process, there have been tools that i've discovered that has made this a bit easier such as Helicon Remote that allows me to remotely control my camera using my Android phone or tablet, very useful when the camera is laying on the ground. I also use this software to automate focus stacking, there are a few useful video tutorials on YouTube by searching "Focus Stacking" and "Helicon Remote".