Most of the times when autofocus fails for me is when there is too much sky in the picture or when there is foreground clutter. I would have to either use the camera's menus/controls to change the focus point or push the button and hold it while reframing the shot so that the camera focuses where I want. If I was shooting a sunset or a similar scene where most of the image was sky that autofocus won't track, I'd change to manual focus.
Then, I'd have other problems to deal with. I would have to restore the settings or reactivate autofocus before the next shot. If I forgot to do that, my next couple of shots would be out of focus until I remembered to put the camera back to its normal settings. If I used the "push and hold" trick, I take the chance that my exposure would be wrong because automatic cameras often lock focus and read the exposure at the same time. If I reframe the shot while holding focus, the scene is likely to be lighter or darker.
This could all be circumvented by putting the camera into manual exposure mode but, why the heck would I want to buy an expensive, automatic camera only to have to put it in manual mode all the time?
Yes, I like automatic cameras... SOMETIMES... but I want to be able to use them manually just as easily as I can use them in automatic mode.
I would much rather have a mostly manual camera that has some automatic features that can be activated when you want them instead of an automatic camera that needs to be defeated when it doesn't behave the way you want it to.