I used to jungle a lot actually, I just gradually realized I sucked at it.
Here's the thing, beyond the simple balance thing, being aware of when lanes are gankable by a given jungler is really difficult for me or when the enemy team is gonna gank.
As midlane I just feel powerful enough to just force it, and maybe that's because I've been play ap eve mainly when I got on this roaming mid binge, but it's also easier to realize when a lane is gankable because when you clear a lane you don't have to worry about going to the next jungle camp so it's easier to check the lanes.
Probably an issue of being bad at multitasking and just something I need to work on.