I can't give you a hard reason. I guess when I learned C all examples were like c=yesno?1:2. So I guess I stuck to it and never thought about triggering an action with side effects that way.
So as an example of doing both, consider following Java pseudocode (simples example that comes to my mind now):
Foo value = someCondition()
? map1.computeIfAbsent("key", defaultValueProvider)
: map2.computeIfAbsent("key", defaultValueProvider);
Foo value = ( someCondition() ? map1 : map2 ).computeIfAbsent("key", defaultValueProvider);
For clarity, let's rewrite it as:
Foo value = someCondition()
? map1.computeIfAbsent("key", defaultValueProvider)
: list1.get(42);