It is because of MC's custom skin UI, I suspect.
My suggestion doesn't really solve your problem, but it would make you not care anymore. If you have two monitors (or more), you should really at least try out
UltraMon.
Assign a keyboard shortcut to the Move Window commands (I like Control+Alt+Left/Right Arrow keys) and you'll never care again.
PS. I use UltraMon, but I've been meaning to try out
DisplayFusion for a long while too. You might want to try both, they're similar. It seems like DisplayFusion gets a bit better support and more frequent updates. I'm not sure which is more powerful...