I quit using leashes after a couple of years of paddling, right around the time I switched to Greenland paddles. I’ve spent a fair amount of time getting pummeled in surf and rock gardens and have only had my primary paddle torn from my grasp on two occasions. In both cases, I retrieved my spare (a Greenland “storm” paddle) from the foredeck and rolled up. From there I extricated myself from the situation and retrieved my primary paddle. If I’d had my primary on a leash, it’s more likely that i would have gotten tangled in the leash or gotten whacked by the paddle as I was getting “Maytagged”.
I have never unintentionally lost contact with my boat, as I’ve trained myself to hang onto it on the rare occasions that I’m forced to wet exit. However, I have practiced “lost boat” rescues while training with other paddlers. I’ve also trained in a variety of reentry techniques and that includes how to secure the paddle during the process. My boats are rigged to allow me to quickly and securely stow a paddle on the foredeck if I need to use both hands for something.
The important points here are training and setting up your equipment properly. When I first started paddling, a leash made sense to me. It doesn’t any longer, so I never use one. To reiterate what Overstreet said above, I don’t know any advanced paddlers who actually use a leash _while _paddling. Like me, they tend to regard leashes as more of a liability than an asset. At most, they may keep a sail-tie leash rolled up on their paddle in case they want to stick one ball under their deck rigging and drop the paddle in the water beside the boat, while they’re otherwise engaged. Most have deck rigging that allows them to stow their paddle, so a leash isn’t necessary at all. We use a variety of different boats and equipment, but we all know our gear intimately and are well-practiced in using it. That, combined with good judgement based on experience is what keeps us safe. Gadgets may give you a false sense of security, but the truth is that you simply can’t buy safety.
Use whatever works for you, but there is no substitute for training, developing advanced skills and tailoring your deck rigging and other gear to your preferred form of paddling. That comes with time, experience and dedication to learning the craft.