You're exactly wrong; either you haven't read the 4e DMG or you never reached pg 42.
I think a lot of confusion in this area comes from the rules themselves:
Environmental effects, attacks, and other forces have no effect on a zone unless a power description says otherwise. For example, a zone that deals fire damage is in no way diminished by a power that deals cold damage.
Environmental phenomena and other forces have no effect on a conjuration unless a power description says otherwise. For example, a conjuration that produces an icy hand functions in a fiery, volcanic cavern without penalty.
All objects are immune to poison damage, psychic damage, and necrotic damage. Objects don’t have a Will defense and are immune to attacks that target Will defense.
Target
Target: One creature
Target: You or one ally
Target: Each enemy in burst
Targets: One, two, or three creatures
Target: One object or unoccupied square
If a power directly affects one or more creatures or objects, it has a “Target” or “Targets” entry. When a power’s target entry specifies that it affects you and one or more of your allies, then you can take advantage of the power’s effect along with your teammates. Otherwise, “ally” or “allies” does not include you, and both terms assume willing targets. “Enemy” or “enemies” means a creature or creatures that aren’t your allies (whether those creatures are hostile toward you or not). “Creature” or “creatures” means allies and enemies both, as well as you.
This last sentence does not imply objects.
What you say is the general consensus of many players who frequent these boards, but not everyone playing the game is a rules expert like many of the people who post on these forums. They read sentences like these where it implies that the target has to be an object in order for an effect to affect it and they play the game for years with that in mind.
Many different aspects of the game rules tend to imply that effects only affect creatures (or the exact targets specified in the power) and since objects are rarely mentioned as targets, they aren't in many player's minds.
Just because the rules experts here on the boards do not read 4E that way does not mean that many players do not play it that way. Perception is often 90% of reality.