99% of the world's hard surface is unprepared. The landable bits of it are mostly gravel, sand or - grass!
1% is tarmac, concrete or buildings and most of that is heavily infested with wires, poles and - people!
If you're going to have an eol then the numbers say it is vastly more likely that it will be over countryside, so surely the sensible surface to train on is - countryside. = grass, not tarmac or concrete!
Having trained, as all my countrymen do (and all those in all the countries around me do) on grass I find it really quite amusing that there are people who consider it somehow odd or hazardous. Do they really suppose they are the only ones to have noticed this? (despite never doing it themselves?) I have a vast admiration and respect for the USA but their parochialism and sometimes utterly inflexible belief in their automatic superiority can be extraordinarily odd. And irrational.