[klabb3]

For recreational scuba this is misleading. The cert is proof of going through training at some point, which differentiates you from someone who has never been breathing under water, cleared your mask and reg, and knows basic buoyancy control. These skills are not intuitive so the main thing is exposure, which the cert proves to a large extent.

Dive shops with more advanced dives ask for total and recent experience as well, and sometimes require you to do a refresher or dive with them once before they take you on the advanced dives (deep, night, high current, overhead obstacles etc). The OW cert is a big contributing factor, but it's not the only data point.

That said most other recreational certs are useless and just a money grab, even including advanced, imo. Shops generally rate OW+30 recent dives higher than OW+AOW, and rightly so.