Yes, I accept that, don't you? I have seen my prayers answered. I have seen laying on of hands healing some people...but not all. I'm sure many of us have seen that. Just because we can't put our finger on why we sometimes can't cast out demons or drink fluoride in our water without getting sick, should not cause us to doubt the promise...only the reason of why God doesn't want to use us as a vessel at times to show His glory. He is the one who decides these things...not us. Even the Disciples were not always prepared in Spirit to do these tasks. I would think as time has gone on, we are more and more distracted and distant from the things of the Spirit.
We may have the Holy Spirit with us today, instead of Jesus, who is in heaven, sitting on the right hand side of God, preparing a place for us...but we can still distance ourselves by our own sins and things that make us not suitable vessels at times. I would think most of the time it is because spiritually many of us are not mature enough to handle the power He has to share. We start thinking of it as our power. Much like Simon in Acts 8.