It says Fireball creates that kind of intense heat, though.
Fireball does not melt metal in a matter of minutes, nor even seconds, but almost instantly - in a fraction of a second.
Don't forget - objects take half damage (divided before being applied to hardness and HP) from Fire, Acid and Electricity. Cold does one-quarter it's normal damage to objects. Sonic does full damage.
Average 10d6 fireball does 35 points of damage. Against an unattended group of objects that consist of a Longsword (Hardness 10, Hp 5), a Large Steel Shield (Hardness 10, Hp 20), a Heavy Mace (Hardness 10, Hp 25), and an Ogre's Club (Hardness 5, Hp 60). 35 damage, halved, comes to 17.5 or 17. The longsword is destroyed (-2hp), the large shield is a bit charred but otherwise okay (13hp), the heavy mace is fine (18hp), and the ogre's club is a bit worse for wear (48hp) but still quite serviceable... however it is also on fire. But that's okay too, as the 1d6 fire damage/round will mostly be shrugged off by the club's hardness of 5 - it'll burn away eventually, but that'll take hours to happen.
There isn't any 'glowing metal' additional damage. The spell description doesn't include any, therefor it doesn't happen. The Heat Metal spell would do that, but you'll also note that the spell takes 3 rounds to 'wind up' before it gets to the really hot stage. Someone would take damage from something they are wearing being on fire (a cloak for example), which would do the normal 1d6/round.
If you wanted to personal-research an Improved Fireball spell that did +2d6 of sonic damage from explosive impact, and acted as a 3rd-round (then 4th next round, and 5th the following round) Heat Metal on a failed saving throw to targets in the AoE - you're free to do so. But such would be probably a 4th level spell, because it would be above and beyond the scope of a normal Fireball.
I am siding with the Anti Mage-Nerfers, for lack of a better term.
I call 'em Whiners; but hey ~ you say toe-may-toe, I say toe-mah-toe. *shrug*
Edit: whoops, forgot a close-bracket.