I wonder how the developers feel that invested in that platform?
I get that MS is in a tough spot. They need the apps to gain traction, but they need traction to get apps. If they'd been faster out of the gate catching up with iphone the market might have split threeways, but by now it's an entrenched duopoly and no new entrant can make a difference. I still think windows phone is better phone OS than iOS or android, but at this point the quality doesn't matter. See also: webOS, FirefoxOS.
Long story short, i think MS is doing everything they can to make the platform work for developers (excellent tools, easy porting from iOS and android, universal apps), but it's just too late. They were there before iphone (windows mobile), but they didn't innovate fast enough when the iphone happened, and now it's too late.
All evidence suggests that apps do not influence which phone a user buys. Users install less than 1 app per month. Windows Phone is unsuccessful for other reasons.
Windows Phone isn't only unsuccessful because of the lack of significant applications, but acting like it isn't a major factor is just being wilfully blind to reality. Microsoft can't just endlessly throw money at the problem. They can't buy their way into popularity if there is no organic momentum that follows, and there isn't.
Windows Phone overall fails to make a compelling argument. But having backseat YouTube, Instagram, Facebook and Twitter clients and no SnapChat or other similarly flourishing services until it's so late nobody cares anymore is a substantial disadvantage.
Finally, that statistic you chose to offer is almost irrelevant. I probably install less than one app a month on my Macs, but that doesn't mean the apps I've already installed aren't extremely important to me. Just because people aren't constantly hunting for new apps doesn't mean they don't use the ones they have.
By that measure, the fact that I've only installed one password manager in five years means I don't like or use password managers. Quite the contrary, it just means I love 1Password and use it every day.
As if WP stats aren't dominated by cheap $0 phones that are also purchased and used as dumbphones and in the case of WP more so because of the lack of apps for the platform.
I hope you realize that the second sentence does not serve as evidence for the first, at all.
WP 8.1 improved the situation with the shared code and PCLs, but it still required two code bases for the UI.
Also forcing everyone to write code for handling application state that should be part of WinRT didn't help.
On my case, I got a Lumia 630 to play around with C++/CX, thinking about the good old C++ Builder days, but even with WP 8.1 UAP, one gets fed up to write something multiple times for the same OS.
Also any half-decent mobile phone developer should know two, maybe three platforms to reach a decent sized audience.
I'm waiting for this handset to be paid off and grabbing a cheap android (Moto G or something)
Edit: Actually sod it I'm going to buy a dumbphone. I just did a 30 second reflection on my mobile device experience over the last decade and it hasn't even touched circa 1998 desktop software yet. I've had every platform and its just a cash sink and privacy nightmare.
Edit 2: Rereading the article actually hs killed the handset for me. I know with stuff like this on the table in the near future my handset is going to be worth nothing so I just did a BIN on the last dumbphone I had on ebay (Nokia 3510i) and will shift this quickly before it depreciates to nothing.