I don’t understand this article. It says “If demand continues along its current growth path, European cities will want 100% of new urban buses to be zero-emissi

I don’t understand this article. It says “If demand continues along its current growth path, European cities will want 100% of new urban buses to be zero-emission by 2026”, but also states that regulation is needed to reach that. If all demand will be for zero-emission buses by 2026, why would the EU have to spend time making it “a requirement on manufacturers to only supply zero-emission buses”? I’m reasonably sure they won’t manufacture them when there’s no demand.