That's all well and good but if you've already spent time creating the damn things then you want them to continue working. What you don't want is the language to suddenly change and make all your stuff either obsolete or so difficult to run that any rational end user would simply give up. I also don't want to have to rewrite my code just so they can continue working with whatever flash in the pan technology is introduced with each time. I believe most languages, including Java, try to ensure that, once you write a program, it will stay working in future versions. That's not the case here.
Webstart suited me great because a user could run an application from the web and/or install it on his desktop with a nice icon. Additionally, I could offer updates and these would be passed out to users meaning I don't have to worry about umpteen different versions of the program being active at the same time. The user didn't need a degree in IT to run them either. As a final benefit I didn't have to send out anything from my server unless there was an software update so I had less bandwidth issues.
I could embrace ASM.js or Emscripten (whatever they are) but who's to say they won't be just as obsolete in a years time. I simply want some stability. If I had a set of features that worked well (webstart) then I don't want all that capability to just disappear over night. It took me quite a while to embrace webstart because I wanted to make sure I wouldn't have the rug pulled from underneath me. I guess I didn't wait long enough
Perhaps in a few years I might understand what lamda expressions are or I might even find some rational use for them. For the moment you'll have to forgive me that I'm not jumping up and down for joy with the latest Java version