Trail/Ulta Running Hydration Vest Use in Climbing?

I have not seen this but was wondering if anyone else has. I was thinking this may be a nice way to avoid carrying a backpack on some multi-pitch routes. Is this the future of fast and light climbing? Obviously won't work in all use cases, such as off-width/chimney pitches, and if a route and weather necessitate carrying several layers, but may be perfect for fair-weather, medium-commitment climbing days where you want to carry a little more than just a rack and rope. Interested in everyone's thoughts...

I use a 6L Merrel running pack w/ hydration bladder for multipitches now. Enough to carry snacks, extra layers, and some other necessities while not being too big or heavy. Not the most durable material though

Blue Ice used to make a running-like pack called the Reach 8 which I currently use. Looks like it’s no longer made in that size.

I've used one of the BD ones quite a bit on long routes, I think they work great! 

I recently acquired a Blue Ice Reach 20, a little bigger but similar style which is nice when you need a little more stuff but it still climbs nicer than most small packs that size.

Liam Coughlin wrote:

I have not seen this but was wondering if anyone else has. I was thinking this may be a nice way to avoid carrying a backpack on some multi-pitch routes. Is this the future of fast and light climbing? 

Several older threads about this on MP, started to become a somewhat common practice around 2019-20ish.

https://www.mountainproject.com/forum/topic/116579280/looking-for-a-running-vest-with-room-for-climbing-shoes

https://www.mountainproject.com/forum/topic/119386120/why-dont-more-climbers-wear-running-vestsor-do-they