Servlet vs REST

Question

I need to create 5 methods on the server side, which will work with binary data. The remote clients are applet and JavaScript. The Client will send files to the server, and

Answer 1

I cannot see any problems on using Jersey and create a REST service. I know that I'm a REST-taliban but it's really simple to implement this kind of architecture using JAX-RS, so... why not?

Your colleagues say: "REST must be created only when it will be used by many apps" but I cannot see how this can be true.Why I cannot create a REST service for a single app?