Shieldless charge on accessories opens up your hat reforge for a lot more possibilities. Max attack power is nice to have honestly, battlefield overture duration is nice to have, dual gun max for gunners, maybe a couple others i cant really think of atm. I wouldnt recommend reforging an accessory until after you have done everything else first really. However not everyone thinks of reforging as a way to profit, at some point character progression becomes incredibly slow and trying to get anything extra is extremely costly and difficult, so reforging accessories becomes a viable option. Saying its useless isnt exactly a correct statement, but it isnt something thats very high on a priorities list for reforging.
Magic Attack is also very useful, it tends to scales to magic damage better than other accessories would, such as Dual Gun Max. Another two that people overlook, or more likely are just too poor to afford, are Vivace Alchemy and Magic Charging Speed. With two accessories and the boots for either of which, you can get the Vivace Speed to 20% base which is the same as overture. I'd love to be in a party with 50% vivace going, it's just too bad it's so expensive and stacks over overture.