A former pastor said once that it was possible to receive the Holy Spirit the way we might answer a friend's knock at the door.
"Hey, I'm upstairs, in the middle of something. Come on in and have a seat."
My teacher Derek Prince used to say the Spirit is a gentleman, and won't force Himself on us. So I can imagine Him taking a chair in the front-room, and waiting for us to join Him, and talk.
It could be that many have received the Holy Spirit that way, and that He's still waiting for them. It may be that our "receiving the Holy Spirit" is actually a matter of His receiving our time, our attendance, our attention...ourselves.