Sorry Eggy! I was being facetious and making light of a very serious subject. Sorry if I offended.
Of course there's a risk, not just to the baby but to all in the delivery suite, mother-to-be and midwives included. But giving birth, for quite a lot of people can be a very frightening experience - akin to dying alone. So, if one person can sit with the dying it seems reasonable that one person can sit with a woman in labour. I remember the time when fathers weren't allowed in the delivery suite. I also remember the time when their presence began to be allowed. They were not welcomed by many midwives who deemed them to be 'in the way'. However, ante-natal care has come a long way since then with many fathers-to-be attending pre-birthing classes with their partner. They receive an education there that makes them a valuable asset in the delivery suite, comforting, encouraging and assisting with prophylactic breathing techniques - time consuming work previously the duty of the midwife. Effectively they can release another midwife for more important things, maybe another birth occurring simultaneously.
Then there's the experience itself to consider. For many it may be the only birth they can be part of. One child families, voluntarily or otherwise, are quite common. There's no re-run, no second chance. The risk of cross infection is minimal in a delivery suite as everybody, including the birthing partner, dad, mum, sister, best friend or doolah, is gowned- and scrubbed up and the air is changed every few minutes. Better than in a side ward or a four-bedder on the ward.