The web is the platform for the PC, this could change but It takes time. Apps are primarily needed for mobile devices.
It better start changing now (and it is...the capability is there or going to be there...Microsoft built it, now will they (businesses and developers) come?). Companies are building in extra features to apps that you can't get on the web or even the PC.
Just 4 examples (I'd have more if I used a lot more apps)
1. Motogp. I paid around 130 Euros to access streaming for the 2015 season. The Motogp app has the capability to multiple screens, up to 4, during streaming. So I can follow the main presentation and up to 3 other drivers or on the helicopter feed. Logging in to the web site I get access to the separate streams but can only view 1 at a time. Sooooo, I use my Android tablet to watch Motogp events. When I'm on travel working and only have my laptop, I make due with one screen. Motogp will be getting an email from me soon.
2. Sony playmemories app. This app lets me wirelessly transfer pictures from my RX100III to????? An Apple or Android device; In this case, to my Android tablet and then uploaded to OneDrive which syncs with my laptop eventually. I do that when are on holiday, traveling light and only want to carry the tablet. I also use that to wirelessly transfer photos on our trip to my girlfriends Sony phone as she likes posting to Facebook. Ya...I'm not totally scwewed since I can hook up my camera to my computer or transfer from SD card.
3. My bank. Won't bore you with the long story, but right now the only access I have to my bank is through the app on my Android tablet. Cannot get in through the website as they do security differently (as I said, long story and I can fix it when I get back to the US).
4. LINE. OK, what about LINE? Does it make sense for them to continue to develop their crappy Windows app or develop using Project Islandwood? I know which app I would prefer to use and I'd use it on both my phone and laptop.
I was irritated enough with Microsoft last August that I decided to go with Android. I picked up the tablet and a phone. The services work pretty well, except, managing contacts. I couldn't add contacts without a third party workaround app. Saving numbers and adding a contact from a text message was very klunky and just getting around the OS in general was very klunky. When I got back to Windows (phone and new laptop) it was like I went from swimming against a 5mph river current to swimming with that same current. ahhhhh.
Like I said, I'm not a prolific app user and even I am running in to limitations. Apps seem to be becoming a big deal. Microsoft, IMO, needs to get out in front of the problem (as much as they can). The 4 apps I mention above could be written right now as Windows 8 or 10 apps and I'd use them.
So....how do you appeal to developers? Businesses/developers have to be able to significantly increase their user base so it makes sense to be able to run on regular Windows platforms. EVEN then, I'm not hopeful of success, but it's worth the effort.