Ross Geller is normally irritating until he had the guts to stand up for his own feelings and proposing to Rachel Greene and they live happily ever after. This may be reason why David Schwimmer (Ross) does not want to go back doing friends – if there ever occurs such a possibility. He feels it’s been ten years now and it’s about time he moved on.

He may have a point there, but the real problem would be that in the series he gets the hottest girl – the one every man would like to have and so a new start in the series may mean that Ross may end up losing Rachel again and all that mad rush to get her back for the next ten years. It can be a pain and David is only being too careful that nothing of the sort happens. It would be a de-promotion if he goes from dating Rachel Greene to losing her to some other new entry character. Of course, things would be different if the new entry was Carmen Electra or Angelina Jolie or maybe even Paris Hilton (men like her).

'Source'