Because then next week you go out, shoot for another 10% growth, and get another 2 users. The following week, you go out, shoot for 10% growth, and get 3 more users. And so on.
The point is to set some concrete, measurable goal for the week so that you know you're always making forward progress. I had a boss once that told me the point of Agile & 2-week iterations isn't to be optimally efficient or to do progress reports for the hell of it, it's to make sure you're always progressing forwards in a well-defined direction. The biggest risk for a project or startup isn't really moving too slowly (unless you're moving really slowly), it's going around in circles.
The point is to set some concrete, measurable goal for the week so that you know you're always making forward progress. I had a boss once that told me the point of Agile & 2-week iterations isn't to be optimally efficient or to do progress reports for the hell of it, it's to make sure you're always progressing forwards in a well-defined direction. The biggest risk for a project or startup isn't really moving too slowly (unless you're moving really slowly), it's going around in circles.