Most of the men I know occasionally get to wondering exactly what is up with women and our love of receiving things like chocolates, flowers and jewellery. 'Chocolates get eaten,' they say, 'flowers die, jewellery is expensive - here, have a vacuum cleaner.'
What men don't get is that flowers, chocolates and jewellery all send a very clear message to the rest of the world - 'someone loves me enough to buy me chocolates/flowers/jewellery', etc. Hopefully said gift also says 'the purchaser has exquisite taste and loads of money' but you can't have everything. ;-)
Jewellery, beyond being pretty (and you know how women love 'pretties') also says - 'I belong to someone'. It broadcasts loudly and clearly that 'I am not a woman alone, vulnerable, unwanted'. And no matter how much our feminist streaks may object to this, all women, sooner or later, want to belong to some man they think is the most wonderful creature on the planet. Some just want to belong to someone, irrespective of how wonderful he is (or not), which may answer another favourite question - 'what is she /doing/ with that guy?!?'.
Rings, in particular (whether of the engagement variety or not), send a very strong ownership message, and this applies to both sexes. They are very noticeable, particularly if said ring includes a gem large enough to black eyes with, and most people automatically check for rings on the hands of anyone they meet that they may be interested in. A ring says 'I''m taken' in pretty emphatic fashion.
For a woman, a ring also provides the owner with the opportunity to brag to her friends (and any other female she encounters) about how wonderful X is, 'look at this fabulous ring he bought me in Y' (it's always got higher brag status if said ring is purchased out of town/country/overseas), 'isn't it gorgeous?' Cue shrieking and admiring noises, followed by either envious glances or sympathetic looks behind her back depending on the size and style of the object in question.
Women, bless us, are never so vulnerable than when it comes to love. We will follow the male of the species to the ends of the earth. We will put up with men doing things that, if our female friends did them, would see us ditching a female friend in a heartbeat. We like the way they look, and feel and smell (provided they're clean ;-)) and most importantly, we like the way /we/ feel, when we have one to call our own.
So next time, ladies, gents and others, that you find yourself wondering why she wants flowers and a fuss made on Valentine's Day, or what a seemingly sensible woman is doing with a right idiot, or why abused women stay where they are (although this is a much longer and more complicated story than I have space for), spare a kinder thought, and have a bit of heart. We really would be more sensible about such things if we could. But then, if we were, you guys wouldn't love us quite as much, would you?