Often, code reuse leads to less bugs and less duplicated effort which leads to more time spent on important things like features and usability.
Except that, I don't disagree with anything else you said.
Fogbugz has their own custom compiler that generates code for the platform of their choice. Facebook has already written their own PHP->C++ compiler. I wouldn't be surprised if they have some team there working on some high-level infrastructure that lets them write UIs and code that gets compiled down to custom Objective-C/html+javascript/AndroidJava/etc...
Except that, I don't disagree with anything else you said.
Fogbugz has their own custom compiler that generates code for the platform of their choice. Facebook has already written their own PHP->C++ compiler. I wouldn't be surprised if they have some team there working on some high-level infrastructure that lets them write UIs and code that gets compiled down to custom Objective-C/html+javascript/AndroidJava/etc...