Why blocking on future considered a bad practice?

Why blocking on future considered a bad practice?

I'm tring to understand rational behind statement For cases where blocking
is absolutely necessary, futures can be blocked on (although it is
discouraged)
Idea behind ForkJoinPool is to join processes which is blocking operation,
and this is main implementation of executor context for futures and
actors. It is should be effective for blocking joins.
I wrote small benchmark and seems like old style futures(scala 2.9) are 2
times faster in this very simple scenario.
@inline
def futureResult[T](future: Future[T]) = Await.result(future, Duration.Inf)
@inline
def futureOld[T](body: => T)(implicit ctx:ExecutionContext): () => T = {
val f = future(body)
() => futureResult(f)
}
def main(args: Array[String]) {
@volatile
var res = 0d
CommonUtil.timer("res1") {
(0 until 100000).foreach { i =>
val f1 = futureOld(math.exp(1))
val f2 = futureOld(math.exp(2))
val f3 = futureOld(math.exp(3))
res = res + f1() + f2() + f3()
}
}
println("res1 = "+res)
res = 0
res = 0
CommonUtil.timer("res1") {
(0 until 100000).foreach { i =>
val f1 = future(math.exp(1))
val f2 = future(math.exp(2))
val f3 = future(math.exp(3))
val f4 = for(r1 <- f1; r2 <- f2 ; r3 <- f3) yield r1+r2+r3
res = res + futureResult(f4)
}
}
println("res2 = "+res)
}
start:res1
res1 - 1.683 seconds
res1 = 3019287.4850644027
start:res1
res1 - 3.179 seconds
res2 = 3019287.485058338