Why doesn't Google Guava Preconditions's checkArgument return a value?

I really love how guava library allows simple one-liners for checking for null:

public void methodWithNullCheck(String couldBeNull) {
    String definitelyNotNull = checkNotNull(couldBeNull);
    //...
}

sadly, for simple argument check you need at least two lines of code:

public void methodWithArgCheck(String couldBeEmpty) {
    checkArgument(!couldBeEmpty.isEmpty());
    String definitelyNotEmpty = couldBeEmpty;
    //...
}

however it is possible to add method which could do argument check and return a value if check successful. Below is an example of check and how it could be implemented:

public void methodWithEnhancedArgCheck(String couldBeEmpty) {
    String definitelyNotEmpty = EnhancedPreconditions.checkArgument(couldBeEmpty, !couldBeEmpty.isEmpty());
    //...
}

static class EnhancedPreconditions {
    public static <T> T checkArgument(T reference, boolean expression) {
        if (!expression) {
            throw new IllegalArgumentException();
        }

        return reference;
    }
}

I just was wondering is that by design and if it is worth to put feature request for that.

EDIT: @Nizet, yeah, checks in methods could be clumsy. However checks in constructors for nulls looks really good and saves a lot of time spent on debugging NPEs:

public class SomeClassWithDependency {

    private final SomeDependency someDependency;

    public SomeClassWithDependency(SomeDependency someDependency) {
        this.someDependency = checkNotNull(someDependency);
    }

    //...

EDIT: Accepting Nizet's answer because I agree with him on side-effects and consistency reasoning. Also if you take a look into Xaerxess comment it looks like that causing confusion amongst other developers as well.