isn't that where the field trials came from?
Sure, but it isn't where they've gone to.
I train as near to positive only as I can, and get a fair result. However Trials in the US have developed along with the e-collar in something like symbiosis. There isn't (IMO) a realistic chance given the present state of knowledge, of competing at the highest level in US Trials without a collar.
This is not to imply that collar training is in any way "better" than the modern alternative; just a recognition that the necessary P+ corrections at distance can't be given any other way; and without such means, the Trials would not have developed in the way that they have. In simple terms Trials in UK are a test of gamefinding; Trials in the US are a test of retrieving. Both are equally valid.
Eug