This is why I said "It's almost always". If you look at my quote, I say all the way back to Basic/Expert. Even OD&D. Almost every version of the game did it this way - they just assumed the players of the game were not such martinets that they could figure out that exploding fire might set things on fire without being told, and the DM's going to make the call not the player.
I don't know why you think it's a positive thing that DM's discretion was taken out of the game for one version, but in my opinion it's not. Indeed all the polling for 5e indicates that players of the game want more DM's discretion put back into the game, and not "a rule for everything".
Fireball (Evocation)
Level: 3 Components: V, S
Range: 10" + I"/level
Duration: Instantaneous Saving Throw: !4
Area of Effect: 2"radius sphere
Explanation/Description: A fireball is an explosive burst of flame, which
detonates with a low roar, and delivers damage proportionate to the level
of the magic-user who cast it, i.e. 1 six-sided die (d6) for each level of
experience of the spell caster. Exception: Magic fireball wands deliver 6
die fireballs (6d6), magic staves with this capability deliver 8 die fireballs,
and scroll spells of this type deliver a fireball of from 5 to 10 dice (d6 + 4)
of damage. The burst of the fireball does not expend a considerable
amount of pressure, and the burst will generally conform to the shape of
the area in which it occurs, thus covering an area equal to its normal
spherical volume. [The area which is covered by the fireball is a total
volume of roughly 33,000 cubic feet (or yards)].
Besides causing damage
to creatures, the fireball ignites all combustible materials within its burst
radius, and the heat of the fireball will melt soft metals such as gold,
copper, silver, etc. Items exposed to the spell's effects must be rolled for to
determine if they are affected. Items with a creature which makes its
saving throw are considered as unaffected. The magic-u,ser points his or
her finger and speaks the range (distance and height) at which the fireball
is to borst. A streak flashes from the pointing digit and, unless it impacts
upon a material body prior to attaining the prescribed range, flowers into
the fireball If creatures fail their saving throws, they all take full hit point
damage frqm the blast. Those who make saving throws manage to dodge,
fall flat or roll aside, taking '/1 the full hit point damage - each and every
one within the blast area. The material component of this spell is a tiny
ball composed of bat guano and sulphur.
Holy 1st edition Batman! Looks like objects are effected here as well.
Shall we continue?
