I have been using a fly fishing vest while detecting since 2011 they work great, I just recently started using a Garrett detecting pouch so I had some place for my pin pointer and hand digger to attach to, a fly fisng vest that is the only down side is there is no place for your hand digger and pin pointer to go, I do still wear the fly fishing vest along with the detecting pouch just because of all the pockets the Vest has and a pouch at the back to carry a water bottle and sandwich while detecting
I have a bright orange one with lots of pockets I wear when hunting farm fields during deer season. It also looks like I'm a utility worker searching for a buried cable. I wear a pouch too.
Not for the pockets, but I started wearing a construction vests after being asked to by a dozer operator so he could see me. A vest seems to take the public eye off of us in public reconstructions. I never use any vests for added pockets. It never crossed my mind.
I bought a cheap one off of eBay for like 12.00 . It actually is working out great I now can carry a little squirt bottle and a folding tooth brush a bit of hard candy and a few other odds and ends . It's super light and fits well.