1. It works the right muscles to fight all the terrible things that programming does to your body. Slouching fixed, wrist issues fixed, obesity fixed.
2. It's crazy fun and addictive. You will make time to go climbing. There is no concept of "I should probably go climbing but..." like there is with the gym, running, etc. If it's physically possible to go climbing now without definitely getting fired, you're going.
3. It's measurable, so it presses the "leveling up" buttons that seem to be hard-wired into dev types. You'll spend years stuck at V6, grinding 4 nights a week in the gym, loving every minute of it in the hope of one day advancing to V7.
4. It gets you traveling. Sure, there's enough rock around town to keep you going on the weekends, and there's some good areas that you can hit for a weekend roadtrip (which by the way will be where you spend every single weekend from here on out). But all the best rock is halfway around the world. You'll save up to spend a winter on the beach in Thailand, summer roadtripping across Europe, and if you ever end up in Paris on business you'll look me up in Fontainebleau and I'll take you out for the single best day of bouldering in your life here in the forest.
Head down to the climbing gym tonight. It'll ruin your life. In a good way.