Because it cheap, has a lot of colourful LEs and made stylistically similar to first Casio G-Shock. It not the most popular Casio model. Though, i think it in top 7.
Plain DW5600 is not popular. Though it is forum favourite recommendation, there are not many of them in the wild.
For every 5-10 solar powered squares you will find 1 DW or less in "classic" colours. I see 5610 more than i see DW5600.
It makes about 0 sense to buy "plain" DW when extra 40$ get you solar, MB6, modern module and better strap. That, if you looking for function. LEs are different story. Nobody buying Mario themed DW5600 because of functionality. Mario is the main attraction and reason why people choose it.
It is cool retro watch to have and true to the roots as it can be. In this sense it total style icon. I think most purchases are driven by desire to have this archaic experience.
Which is totally fine. I love my calculator Casio watch and it gets most attention of any watch i have. Calculator part there is for the style and not really give any functional reason to buy it.
I have two. Plain and LE. Plain i don't wear much at all. LE gets more wrist time due to funky looks and higher quality of strap (less stiff, less sharp edges).
