If you have a lot of tab characters inside a text document or program file, they can be annoying because of how they’re represented differently in various text editors. For example, when you send your code to someone else, is it going to display the same way on their screen as it did on yours? Tabs are a bit unpredictable in this respect, and spaces are a much safer bet.
This is a companion discussion topic for the original entry at https://linuxconfig.org/replace-all-tab-characters-with-spaces/