Why? Even once you figure out ignition, you still have a bunch of engineering issues to tackle. Energy extraction, tritium breeding, reactor longevity, reducing the build time and cost. Hopefully most of that can be figured out in parallel while we inch closer to ignition, but it's not like once we get ignition we can just copy-paste our way to actual commercial fusion power production.
Because going from the science project has finally worked to supplying 10% of the worlds electricity in just 20 years would be a truly incredible pace progress.
