I'm planning to do a post on this soon on our new graphics blog. The subject's a bit complicated, but I'll try to do the short version here.
We've tried a few different antialiasing techniques over the years. There is no perfect one. They all have strengths and weaknesses. The big reason we chose the one which requires OpenGL 3 as the first one we support and document is that it works on a wider range of geometry types. Consider the following example.
h1 = plot(a,besselj(1,2*a));
h2 = patch(4+r.*cos(a),r.*sin(a),zeros(size(a)), ...
In R2014b, both the blue line and the red patch are antialiased if you're using the OpenGL renderer. As you know, the earlier, unsupported technique allowed you to antialias the line in earlier releases, but didn't do anything for the patch.