Rice adds a sort of nuttyness or creaminess, especially if mashed at higher temperatures when some of it is converted to dextrins and other 'mouthfeel' components. Also the part that gets converted to fermentables ends up as maltose, not glucose / fructose - so it gives a quite different flavour than adding sugar or dex.
Originally rice was added to mashes made on the high nitrogen malts of the time (150 years ago and still going strong in the USA). This used up the spare enzymes in the malt and gave a lighter bodied clear beer at the time when affordable glassware became available and ppl stopped drinking out of tankards so clarity was a new factor.
However in the USA it became the accepted taste of beer, and they still use heaps of rice in their mainstreams (as does Corona) even though the rice is probably more expensive nowadays than the malt
![Stick Out Tongue :p :p](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
In the UK however rice became attractive after the repeal of the malt laws in the 1880s. Before that rice (and maize etc) was taxed as a malt, after that it was classed as a sugar and especially during malt shortages in two world wars became basically a malt sub and a cheapener. Again however it became the taste of beer and I often slip a bit of adjunct into UK beers for a 'historical' effect to echo the beers I grew up on. I note today however most UK breweries seem to be back to all malt which is now cheaper, and only use sugar as a gravity adjuster.
Endeth the essay, I'm on holiday so WGAF :lol:
Edit: yes as L-bomb says it doesn't add heaps of body as such, but a nice smoothness and definitely not the thin twang you can get from over use of sugaz. And it can give you a couple extra ABV without the beer becoming cloying if you are a 6% + fan.