Yeah, I grew up on a ranch in Oklahoma. I had show cattle and pigs in the 4H and FFA for the full 8 years I was eligible, did local, state and national shows. The stuff people do to make their cattle look like that and be show ready could get pretty damn ridiculous.
As far as fun or profit goes, technically it's for both? I mean, I'd argue it's more so the parents can give you something to do. An extracurricular activity like a sports team or something. If you do well it can definitely be profitable since at the end of most shows the best of the show get to show off for a donation auction. Local shows tend to pay the rather expensive bills if you do well, but state and national shows can net you a hell of a lot of money if you do particularly well. The bigger shows tend to be incredibly competitive and have a habit of the higher ranks going towards group purchased cattle though. I recall more than a few winners of the state shows having steers and heifers that cost the upwards of $20k. For national competitions I recall at least one grand champ that originally cost $60k.
Steers get slaughtered at the end of the season. Heifers get bred and if they were particularly good, they are usually bred for more show cattle. There are also shows for Bulls and milk cows which are similar, but have very different goals for showing. There are also a shit load of other show animals including ducks, chickens and so on at state level and up shows, but I'm not as familiar with the non cattle examples.