It's that way in a lot of games, both forum and face to face, the player/s decide on a course of action or to go somewhere/do something, then react to the GM's narration of the outcome of that effect, or description of the next scene.
Players generally are in control in that they choose where to go/what to do at any given moment, but they rely upon the GM to shape the world around them and describe the stage on which they take their actions.
In face to face games it takes mere moments for a GM to describe a room, or detail the quality of a sword, the response to question directed at an NPC etc..
In a forum game the scene often hangs on the GM's input and narration of how their previous actions have effected the scene before players can take their next action. This delay slows the pacing some, (as does waiting for the response of other players in the scene before the GM can provide narrative, along with players waiting on each others responses.) but the story crafted in a forum game is every bit as rich and enjoyable as those in traditional TT.