A very good question.
Like many things - a simple question but the answer is somewhat complex.
I’ll start with a distilled, highly distilled and curated response then, for those that have a few more mins to kill (at the time of writing planet earth is exposed to the Corona Virus so some of us have plenty of time at home) I’ll enter a bit more detail below.
First answer is - people choose Japanese knives because they have chefs knife or Japanese knife obsessive compulsive disorder (OCD). Quite simply - they are looking for the sharpest and hardest knife blade on the planet and the Japanese blades are the winners. If you’re in a rush there is the answer to your question.... but there’s more to it....
Japanese knives have some downside.
Firstly, in pursuit of the toughest, hardest steel on planet earth one way to move in that direction is to add carbon to your steel. The addition of carbon increases steel toughness and hardness BUT on the downside it reduces malleability and increases corrosiveness. Japanese knives follow this process.
For example German or Swiss steel knives (like wusdorf, Victorinox) the carbon will be around 0.5% where as Japanese blades will be double for most (over 1% for AUS10 or VG10) and 6x as much on the extreme (3% carbon for ZDP189 or MC66). This cranking of the carbon means a super hard, tough blade edge however it does lead to higher corrosiveness and greater likelihood of chipping.
So how do we counter this problem?
If you want a knife that’s super sharp you first add carbon - just as the Japanese knife steel manufacturers do - then you need to learn how to maintain it and commit to do so - for the life of the knife (lifelong if you follow these steps)
First, you don’t put your knife in the dishwasher. Don’t do that with any knife but long lasted water exposure to a Japanese blade is a disaster. Keep it dry. While it regularly. Keep it dry. When your finished dry it. Dry it.
Secondly, the Japanese blade needs to be periodically sharpened on a wet-stone. Not a rod. A wet stone. The stone must be wet!
When using a rod you are basically re-shaping it. This works well with European steel but is not the process for Japanese. With Japanese steel you have micro chips that periodically needs to be removed. This is done through wet stone sharpening. The stone itself needs to be wet to keep the steel temperature down as sharpening is performed. So to keep the knife we love we must learn to periodically wet stone sharpen the blade - or find someone who can do this for us.
So back to the start - if you want a Japanese knife - you must concede to knife OCD, learn to love taking care and keeping dry and become a master sharpener.
That’s why some love Japanese knives.