What is an enrichment class?

So, I was having a chat with a Singaporean girlfriend who's been in the UK as long as I've been and is actually heading back to Singapore for an initial 6 months whilst her British husband's working out there. She's had to frantically locate some nurseries/playschools for her 4 year old and her 2 year old.

She reports that it's really quite expensive (even though we complain enough over here in the UK that for fulltime nursery daycare, it costs us nearly £800/month), she's going to be paying something like S$1500/10 weeks (£600-700/10 weeks?) for 3 hours of care per week. That's ALOT of money, given that that's only for 3 hours of daycare!!! hm. And apparently, if she wanted 'enrichment' classes, she'll have to pay extra. Apparently enrichment = art/music/singing/dance classes.

My question: Why is it that such classes are deemed 'enrichment'? Why aren't they part and parcel of the early-years curriculum? We're talking about a 2 year old and a 4 year old for goodness sakes. We're not talking about having to deprieve a school going child of his math classes just so that he can do a bit of drummming, or a bit of painting!!! Shouldn't this be offered anyway? not necessarily every day, or even every week but surely they could do it??

At G's nursery, he comes home with a report sheet everyday. Apart from recording his poos and wees, his naps and what he's eaten, we also get a record of what he's done. They tend to include singing, painting (they were making some collages, painting the hungry caterpillar), 'investigative' work (they found a spider and looked at it under the magnifying class, outdoor play, dancing, home economics (he makes his own puddings of biscuits, banana-choco, fairy cakes - yes, he helps to measure out the ingredients).... and so on. It's exhaustive! and that's NORMAL curriculum.

hmm.