I couldn't tell you why they are three releases behind. I did remind them of this several months ago, but I don't know what their schedule is (I'm not on the side of the fence that takes care of these things). Perhaps it's a low priority, and as long as it doesn't break, they want to leave well enough alone. I don't think they've had any significant problems with 2.0.11. I expect to eventually see them upgrade to 2.0.14+. I wouldn't expect a jump to 2.1 any time soon, unless PHP 7 doesn't work with 2.0.
I don't mind keeping my SMF at the latest level (2.0.14), and have had no problems with the one-button upgrade, even though I have half a dozen mods installed and a dozen or so custom code changes (including putting the last DB error timestamp in a separate file, so Settings.php never gets mangled, and member-selectable timezone rather than just an hours offset). Of course, I take a file and DB backup first, in case anything goes wrong.