I am not entirely sure that these do not exist purely as an instrument to torment me as other people open them and flash me their good fortune
But, you say, cant this delay be used against you by the opponent to gain knowledge about set cards? No, you can both suppress the (actual) prompt when you have something on the field, or open a fake prompt at all times
The preemptive semi-limitations of the two strongest cards should already convince you of that
With enough mana, that might be enough to do something with the one (or both) that goes back to your hand, like have an answer to a very tricky problemsuch as a Counterspell or a Fog
Song of the Dryads is around $2.25 and the rest are all under a dollar
That said, there are a few variations to keep an eye out for similar effects