I agree with this. I'd only add that presenters etc sometimes have the advantage of being a face people recognise and feel they 'know' and like (especially if they're on a trusted news programme or something like The One Show). And of being the plucky underdog, which British audiences seem to love!
The 'dance experience' thing is a red herring and just whipped up by the media every year to get sales and clicks. People who are technically the best (Ashley Pussycat Doll, Alexandra Burke etc) almost never win; the voting audience can spot a ringer and tend to want to support those with less directly applicable experience when it comes down to it.