As a defensive player with a loose ball on the floor, you have several options. First would be to grab it and save it from going backcourt, if you have someone you can pass to, or if you can stop yourself. Second is to either get a foot to the line or let the ball get backcourt, with the obvious risk tha the offense may get there first.
The third option, assuming the offense had established team control and the defense never had team control before it started rolling, is to tap the ball to space in your backcourt. You have not established player control (unless a ref deems it so), so there is no team control by the defense, and therefore the backcourt rule is not applicable. You are free to go get it in your back court. The last option is to tap to a space where you can get it in the front court, not worry about stepping over the line after the tap, re-establish yourself front court, and pick up the ball. This is pretty hard to accomplish.
This is why it is so easy both to ref and play basketball.
There are so many options
