I have many reasons for preferring CW to all of the other modes (and yes, I will occasionally work digital, and I work SSB and FM on the satellites).
First, it is mentally stimulating to decode the dits and dashes and have a message take shape. Indeed, I saw an article a while back that said that learning morse code builds up gray matter in the brain (I need all the gray matter I can get since I was repeatedly told in my youth that I lacked it).
Second, it is obviously more efficient in terms of weak signal work. It was FT8 before there was an FT8 mode.
Third, it is easier to build your own equipment for CW as opposed to most of the other modes.
Fourth, a good CW QSO is a joint operation between the two operators. For the conversational part, both operators have to have decent fists, have to be able to copy well, and have to synchronize their skills to each other. It's a delicate dance that we do with each other when we have a QSO that goes beyond "5NN, name and QTH". And it feels professional and wonderful.
And, finally, when I've had a good long ragchew with someone, I invariably feel enriched with the sense of sharing and accomplishment with my fellow ham.
I will never forget a CW QSO I had over 20 years ago with an 80+ year old ham who had lost his XYL the year before. He told me that, without his hobby of ham radio, he wouldn't have much to live for, since he missed her so much. I know he was in tears when he sent that, and I was in tears copying it. Somehow, I don't think that intensity would have occurred if the QSO was on a voice mode.
Someone earlier mentioned you can't hear accents on CW. Doesn't that make CW the great equalizer? There have certainly been QSOs between Oxford scholars and "good ole boys", between people of different races that may not ordinarily mix (not that I condone antagonism between races - I'm just saying CW has probably dropped a few barriers for people).
This list is not meant to be exclusive.
