In such situations I've actually moved the speakers out into the room a bit. As has been said, the biggest factor (in terms of set up) is the distance from the mic to the speakers. But the other reason is that quiet speakers get scared when they hear their voice amplified and back off even more. The closer the speaker cabinets are to the presenter, the more aware of them they are. In order to get them up on the mic, you want the system to be as quiet on stage as possible.
As was also said, people in the front rows will hear some sound from the presenter. And if the SOS are a couple of rows back up high and pointing to the rear of the room, some sound from them will still reach the front rows. Maybe not the ultimate in clarity and HF but usually intelligible. And the extra gain and bit of proximity will really help the rows further back.