The market still wants Win32 because metro/uwp was crippled, limited. Or more precisely, apps built on the new platform were not powerful. Microsoft Edge which was built as a tech demonstrator still had to rely on private APIs.
Second reason: The only place to discover and install the new apps is on the store which has bad, awful, pitiful search to using google or even bing. I don't know why MS doesn't leverage Bing in the store.
Lastly, in my locale and surrounding countries, sharing EXES is still necessary because of internet speed and data limits.
Ms removed the Small text size download links in the store. And their TOS prohibits development of apps to download them.
To give a context of importance of UWP/Metro installation files downloadability:
A customer walks into my shop and buys a new Android phone. And after that asks me to fill up the phone with apps like dictionary, bible, WhatsApp, anti-virus, games... for a fee.
The same happens with Windows desktop portion. But this isn't feasible with the new apps - internet cost and download time.
And it was one chief reason why Windows Phone didn't take off - at least in my country.
A friend return a chrome book last year simply because he couldn't just copy apps from others (like on windows).