the person who wrote the text for fireball clearly envisioned it as not damaging items which are worn or carried, and spent extra effort to specifically communicate that. That is the intent of the fireball spell. You could argue that the page 87 ruling has other intent, but the spell's intent is unambiguous. If it meant something else, it wouldn't have those words.
It's not unambiguous!
Here's one way it could have been made unambiguous:
The spell ignites flammable objects that are in the area of effect and are neither worn nor carried by a creature. It does no damage to any other objects. I'm sure there are other variations that would have the same consequence (eg judicious use of "only").
But no such wording occurs. You are extrapolating an intent and a message which is not the only plausible thing being communicated. As [MENTION=6787503]Hriston[/MENTION] has just pointed out, for instance, and as I am inclined to think, the significance of calling out these things specifically is
to take the question of their ignition outside the realm of GM discretion. Which would still leave other objects within GM discretion (as per SRD p 87).
You don't call out something specific like that unless it's necessary. Since there are rules for destroying objects, there is no need for the statement in fireball unless those rules were not appropriate.
But there are any number of reasons why those rules might not be approriate: for instance, if they invoke GM discretion and - when it comes to fireball's effect upon non-worn, non-carried items you don't want the GM to have discretion.
Similarly, if the writer of fireball had intended it to destroy objects both attended and unattended, he would have said so. By calling out unattended only, he is excluding attended items.
I could equally say: had s/he wanted to state
and nothing else is affected, s/he would have said so. But s/he didn't.
Which means it is a matter of interpretation. Your reading is no more "automatic" than mine. And I think mine has the virtue of reconciling the spell description with p 87,
and of reducing absurdities in the fiction, like goblins being burned to death yet their clothing being completely unsinged.