Specifically with Eldritch Blast, you could use the special ability that pushes your target to move objects at a distance, and that could get very difficult to adjudicate when you're throwing out three blasts in a round. With that kind of useful at-will magic, I'd be more prone to try and solve obstacles with an impromptu game of Portal than in the usual way, and that's not something that an inexperienced DM could deal with very easily.Is there any good reason not to let spells like Eldritch Blast or Ray of Frost target an object when other spells, like Fire Bolt, can?
Can you define a "good reason?"
It's RAW, and that's a pretty good reason for most rules questions at my table. I think there's inherent value in playing the game as closely to the original parameters established by the system developers.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.