I am creating a vector artwork and finalising it to print. I don’t usually use illustrator and have discovered transparency flattening. I was wondering why its used? If its an old school preset no longer needed?
You dont need transparency when printing (a print has no transparency) so quite many prints shops require you to flatten the transparency before you print as it ensures least amount of errors. (this is done automatically on PDF save though but its the same tool with same settings).
Second reason is export. Sometimes you take artwork and move it to less capable systems. Then you can use transparency flattener to retain your graphics. Such systems include Visio, Powerpoint, LaTeX etc.
Third reason is if you want to edit the compound color and other editing tricks that rely on the flatteners features. Sometimes you can use this for cleanup. Sometimes for complex selections.
Fourth reason is to retain art integrity when sharing to others. By flattening the artwork you make the artowrk harder to compromize. This reduces the editability of the file while retaining print fidelity.
Fifth reason to be backwards compatible in workflow and file formats.
Basically all the reasons that existed when it was first introduced. If it was obsolete to you then then its obsolete today. You might never need it for anything as its automagically applied for you but that does not mean its obsolete.