For example, you can compare and see the result of every strategy you did on every bet and this will help you to maximize your profit by using the best strategy.
There are people who don't maintain a spreadsheet because they don't really know the benefit of doing this or just don't know what to compare.
For sports bettor, this is a good example posted by.
Everything is mentioned in the file: bookmaker, which sport, selection, bet type, stake, odds, ...,
Usually, people do spreadsheet in this particular type of game, for me as a gambler, I never have a spreadsheet of other type of game.
Anyway, that's still up to the specific gambler since all posted here are just personal opinions.