Because there are other factors at play. No-till is mostly about sustainability of farming. Humans often don't optimize for the most sustainable option but for the option that's most profitable (or perceived to be most profitable) _right now_.

Tilling and using crazy amounts of mineral fertilizer definitely improves yields. But it will, in the long term, also kill agriculture to a large extent if we're not careful. We're not talking about highly speculative outcomes here: The data is pretty clear and everyone with even a large pot and some soil can run the same experiment at home and come to the same conclusions.

Farmers need to survive, they need to earn money, they will obviously optimize for short-term yield. We shouldn't judge them for this, but we _should_ find ways to solve the issue, ideally together with farmers.