Earlier this year we did a sand and finish job for a whole house that had tons of urine stains. Animal urine can be a pain to get out of the floors because it soaks deep into the wood. After sanding it, the next day the spot will smell and become wet again. The best way to get rid of urine stains is to cut out the stain spot and replace the wood. If you sand one spot too much it will create a dip in the floor.
This is what happens when you try to sand a floor with a deep urine spot.
Instead you can do something like this. The outcome looks way better than trying to just sand it out.
Although some spots you can't get out, a sand and finish sometimes is better and easier than replacing your whole floor. If you have a engineered or solid wood floor that is starting to become scuffed from people walking on it over time, or perhaps dirt has set into the top layer of the wood, then sanding the floor and having it refinished is a great option.
We did another job where the owner of the house just wanted their old floors to sparkle again. This was a good example of when sanding and putting a finish on the wood can be super fast and cheap way to make it look like you bought new floors. Especially during holiday time of the year when you don't have much time or money to spend on your floors but want to impress the family, a sand and finish might be the best option.