It's the extra layer of convolution. It's necessary in a browser, but when circled back to the server, it's vestigial.
With Deno, you're using a classic OOP inspired superset of JavaScript, transpiling it to JavaScript, and running it in a JavaScript engine on a server. That's only necessary in a browser.
On a server, if you don't want to use JavaScript, you can just directly use a classic OOP language, and dispense with the whole extra frontend transpilation abstraction.
Unless you're a frontend-only webdev, and, understandably enough, you don't want to learn a classic OOP language, which I believe is the real reason.
Or, at least I hope so, because the only other possible reason is mass obliviousness, and that's horrific.
I have a theory that TypeScript was not actually invented for frontend developers, it was created for non-frontend developers who were forced to deal with the frontend, and hated JavaScript.
That's also why I think it's very funny that JavaScript developers are starting to use TypeScript on be backend, i.e. Deno.
You are using the patch to JavaScript that backend devs needed to make JavaScript more like backend languages in the very place that the languages it is trying to be like already exist. It's ludicrous.
With Deno, you're using a classic OOP inspired superset of JavaScript, transpiling it to JavaScript, and running it in a JavaScript engine on a server. That's only necessary in a browser.
On a server, if you don't want to use JavaScript, you can just directly use a classic OOP language, and dispense with the whole extra frontend transpilation abstraction.
Unless you're a frontend-only webdev, and, understandably enough, you don't want to learn a classic OOP language, which I believe is the real reason.
Or, at least I hope so, because the only other possible reason is mass obliviousness, and that's horrific.