I remember back in the day setting up cross compiling was horrendous though, so I agree, I just don't think it's the only reason. These days all you do is set a flag and rerun "go build", it's stupidly easy, as far as compiling goes.
The other two things that come to mind is that on the web users expect things to look different, so the fact that your cross compiled app looked/behaved like ass on at least one platform unless you basically rewrote the front end to conform to each platforms user interface guidelines (aka write once, rewrite everywhere), meant that websites could look more how the company making the website wanted it to look, and less like how Redmond or Cupertino-bases companies wanted it to look.
The real killer feature though, imo, was upgrading of software. Customer support is a big expense that ends up sinking developer time, and if you got bug reports and you fixed the problem, you'd keep getting bug reports for that issue and the CS team would have to figure out which version the customer is on, buried three menus deep, before getting them to upgrade. The website, however is basically always running the latest version, so no more wasting everyone's time with an old install on a customer's computer. And they showed up in metrics for management to see.