I think we are all aware (one would hope) that we are not in America, but however I can see where they are coming from.
Quite a few US networks have fewer main presenters, where as ITV News seems to have quite a lot of "Newscasters".
On one day from first bulletin at 5.30 to the news at ten you could have a total of 6 different presenters covering 4 bulletins, something you probably won't see over on NBC in America for their main network news bulletins.
Well, aside from the breakfast programme, don't the US networks only have one newscast per day? I'm sure the last time I was in the States ABC, CBS and NBC had an evening newscast at 1830 and news at other times of the day was local.
Anyway, what's wrong with there being a variety of presenters? Everyone seems to criticise the BBC for over-using Tim Willcox, so surely some variety is better? And in any case, the BBC is a much worse offender for having too many newsreaders than ITV. The only main newscasters I can think of are Mark, Alastair, Mary and Julie - between them they pretty much cover most weekdays. You can't count the weekend bulletins and the Morning News because more often than not they're covered by freelancers, which is not unusual - even the BBC use odd faces at weekends.
Have you ever thought that there's a lot more to a newsreaders job than just that 30 minutes on air? There's a lot of preparation to be done: meetings to be had, interviews to be recorded, scripts to be written, rehearsals... the list is almost endless. On the few occasions I've visited ITN I've seen Mark Austin in the newsroom in the early afternoon for News at Ten. Can you imagine if one newscasting team was doing both the Evening News and News at Ten on a regular basis? They'd be constantly in and out of the newsroom and studio for hours on end! You might say that Alastair Stewart regularly does the Lunchtime News and Evening News without too much trouble, and both he and Katie Derham did the Lunchtime News and London Tonight. Well, in both of those examples, there was a co-presenter for the later programme who could get involved with preparation while the other was absent reading the Lunchtime News. Newscasters don't just twiddle their thumbs between bulletins - hence why they get paid so much!