Autofocus can be very fickle Eric, especially on a subject that is very contrasty, or where there are lots of elements in the scene (giving a large range of focal objects or depth of field), as in bunches of flowers, large displays or just a very large-bloomed flower. The camera can get a bit confused as to what to focus on - usually being the nearest object to the camera lens.
As you rely on autofocus, you have found a good work-around that works for you. And that is a very important part of photography. It doesn't really matter what methods you use, as long as you 'get the shot'
