Cameras and I go back several decades. I just do a lot of camera stuff automatically without even thinking about it.
Sometimes I have a hard time understanding the perspective of a beginner photographer. Like just what is this fascination many beginners have with manual mode? I've seen some here that have no idea of the exposure triangle and just blindly spin dials hoping the resulting photo isn't cr@p. "Exposure meter? What's that?"
Don't get me wrong, I use manual mode when appropriate, typically for me when I use a flash. Manual mode can also aid the beginner's education when used in a systematic way.
So why does that big "M" hold such a fascination with a beginner? Did someone tell them the photos are better or something?
To answer your last question first, I suspect it's to do with M mode having an 'expert' cachet, that you can't use it unless you're an expert, so using it shows you to be an expert.
More completely, exposure management is essentially about choosing a balance of depth of field, motion blur and something else. I say 'something else' because there is not complete agreement on what it should be, but we'll deal with the other two first. As we know, DOF is controlled by the aperture, motion blur by the shutter speed. M mode has the nice simplicity of giving you a wheel for each, while the other modes generally still involving you using the two wheels (one for aperture/shutter speed and the other for exposure compensation, or one for program shift and the other for EC) - it's just that the effect of the two wheels is somewhat less direct and harder to fathom.
Now for the 'something else'. Mostly camera UIs are designed so that the 'something else' is output image brightness, that is, you are trying to balance DOF, morion blur against output image brightness, within a general playing field that you selected when you set the ISO. What setting the ISO actually does is determine the target exposure, so this comes down to selecting a combination of aperture/shutter speed that, along with the light from the subject, gives the exposure that you chose when you set the ISO.
For others (myself included) the 'something else' is image noise, given that the more exposure you have the less noisy the image. So people like me are trying to get the biggest exposure that can go with our needs for DOF and motion blur. The auto modes are not designed for this something else, they will try to control exposure according to selected ISO, not to maximise it, so M becomes the mode of choice if this is your 'something else'.
