Tillage before motorized agriculture was much more superficial. Besides, there are many examples of no-till traditional agriculture, or adjacent versions such as agroforestry.

The no-till experiments started when the destructive effects of deep deep plowing started to appear (e.g dust bowl). It's a clear sign that society realizes that the local optimum isn't sustainable.

No-till is actually quite technical if done right, often requires some level of herbicides or way to cover the soil.

The argument "why didn't we do it before" is moot, before the 19th century midwives didn't wash hands either, why are they even do it now? Right?