To build off what dgallo said, i like my hazies to finish around 1.020 or so. If I'm using a high attenuating yeast strain I may add some maltodextrin (to the boil, 10 mins) or dextrin malts to the recipe to raise the FG. For example, if I have a recipe that predicts my FG at 1.017, I'll add maltodextrin to the recipe to raise the FG to 1.020 - 1.022. You can use calculations like dgallo stated or most brewing software will do it for you. Maltodextrin is nice because you typically use it in the boil so you don't have to worry about mashing with it and worrying about efficiency.
I've read some people back sweeten beers with it post fermentation. I personally would be way too afraid of O2 introduction to attempt that.
To summarize, its just another tool in our tool belt to control the outcome of the final beer. You could control FG with mash temps but you would most likely need to use more malt and that introduces new problems, especially if your grain bill is already high in adjuncts like oats and wheat. That's probably one of the main reasons Sam from Brujos uses it. He said he gets really bad efficiency as it is, if he wanted to raise his FG without maltodextrin it would require higher mash temps which would result in lower fermentable sugars and a lower abv.