This seems to be something I have been noticing a lot lately.

Artists who have a single out, that is not doing too well in the chart and in need of promotion seem to use their slot in TV to promote a known song of theirs or a previous hit instead of the current one.

An example of this is Little Boots. She sang "Remedy" her previous and biggest hit on CIN which is a few months old, not realising she has a new single out "Earthquake" which is really flopping in the charts.

Why do artists do this rather frequently? Surely, people want to hear newer songs.

I'm guessing it's because they are performing to loads of non-fans who will all want to hear something they actually know as oppose to something they don't.

If it was Janet Jackson performing i'm guessing the majority of the audience wouldn't care too hoots about Make Me but would know probabbly go wild for Rhythm Nation or Together Again.

I know what you mean though. Songs won't sell unless they have been heard, and if artists don't perform them nobody will hear them.

No idea. Maybe because of the occasion, Little Boots was allowed to sing whatever she wanted and decided she'd rather sing 'Remedy'? If Earthquake was flopping, and there's plenty of new big releases coming out then what woud be the point of trying to increase sales for it. It wouldn't exactly do much help.

I noticed Sugababes also sang 'Get Sexy' rather than their current top ten hit 'About A Girl' and Pixie Lott sang her previous #1 'Boys And Girls' rather than her current top twenty single which is only on downloads. If she performed 'Cry Me Out' it would have probably have reached top ten and it would have really helped for when it is eventually released.

I'm assuming it's more to do with the occasion (a charity event) than any other reason.

Actually I prefer it when they sing familiar songs rather than brand new ones. Shirley Bassey was on Strictly Come Dancing yesterday and sang something I'd never heard before - I would have much preferred to hear one of her famous ones as I think hearing a song 'we all know and love' adds to the atmosphere. Particularly on something for charity like Children In Need I am very cynical when they perform a new song as it then looks like nothing but self-promotion rather than contributing to a cause.

I think it is because it's what people expect them to perform. Most of the time at places like Glastonbury they'll perform mainly their hits with a smattering of maybe one or two new songs. This gets people who haven't heard them before to know their biggest songs and maybe go out and buy an album. Most artists see an increase in sales after festivals they've performed at. The same can be said for X Factor as well, hearing someone perform can get a few new fans or people seeking that persons back catalogue by listening to them via streaming services or the likes of Youtube.
Performing new songs can dicey, it's uncharted territory and could seriously backfire, and should you be a new artist trying to get a foothold and push yourself forward it's suicide.
This is why some artists now see X Factor as way to get their music across and of course a themed night of their is pure gold.