One reason, which is a bad reason, is that many people just don't like to document and handle errors. Instead of being happy that the compiler is telling them that they forgot to handle or declare an IOException from this call, they get annoyed that it's yelling at them "for no reason". This is simply lack of understanding/care for how you program.
The other reason, which is actually a problem with the language that could be fixed, is that Java doesn't allow functions to be polymorphic in their Exception types, like it does for argument and return types. This makes higher-order constructs very annoying - for example, `stream.map(Function)` should `throw` the same Exceptions that `function` throws, as should `Arrays.sort(array, Comparator)`. Without this capability, you end up with an extremely ugly and brittle pattern of doing:
//V foo(T x) throws SomeException();
Stream<V> bar(Stream<T> stream) throws SomeException {
try {
return stream.map( (x) -> {
try {
return foo(x);
} catch (SomeException e) {
throw new RuntimeException(e);
});
} catch (RuntimeException e) {
if (e.getCause() instanceof SomeException) {
throw (SomeException)e.cause();
} else {
throw e;
}
}
}
Stream<V> bar(Stream<T> stream) throws SomeException {
return stream.map(Foos::foo);
}
Usually, what happens is that you call some library code (or some code that a teammate wrote) and that code will declare an IOException or something like that. In many cases, there's no point in handling that, as that file that you're trying to open or similar isn't supplied by the user but e.g. a static resource. That's the entire point of the article, that panicking when encountering a violated precondition is totally acceptable.
The unchecked vs. checked exception distinction also suffers from the fact that it's usually the call site, and not the declaration site, that knows whether an exception is recoverable or not.
Java checked exceptions would be fine if it had something like "unwrap", which just converts a checked exception to an unchecked one, but it doesn't, and that's why everyone kind of hates them.