AbdulAlhazred
Legend
As I may have mentioned, my impressions of 4E were formed entirely within the first six months of release. And I already admitted that controllers might be an exception to this, since their powers tend to be more situational.
In this case, it's actually more like a guideline to help the DM adjudicate. If you're a paragon-level party, and there are only heroic-level fire sources around, then your improvised fire attack might deal less damage than you were hoping.
Page 42 allows for more than 'do some damage without expending a power' of course. Just take a fire for example, you could force an enemy into it with a power, doing some extra damage (its free damage, why not), and keeping them there (probably another power, to take ONGOING damage is good too). These would be worthy things at paragon, though possibly not enticing enough to bother with depending on the situation. You could also throw fire, maybe using your Thunderwave to blast it into the faces of bad guys (good for an extra 'blinded UEONT' perhaps).
Ultimately though this gets back to my words on encounter styles. It IS incumbent on the DM as primary author of the environment to produce a complex, dynamic, and interesting environment in which exciting action-adventure scenes can be played out. If he's filling boring rooms with nothing but little braziers that do 2d6 damage for terrain then indeed the game may get boring.