The issue with current early detection methods is that they tend to cause more harm than good at population scale. Between getting dosed with radiation in the process, false positives causing at best psychological trauma if not unnecessary treatment, and it's hard to tell if you just detected a cancer you'll die with instead of dying of - and thus another form of unnecessary treatment.
The blood tests remove some, but not all of that. Yes, for any arbitrary person it might be lifesaving, just like current methods. But at population scale it's not a panacea.
The issue with current early detection methods is that they tend to cause more harm than good at population scale. Between getting dosed with radiation in the process, false positives causing at best psychological trauma if not unnecessary treatment, and it's hard to tell if you just detected a cancer you'll die with instead of dying of - and thus another form of unnecessary treatment.
The blood tests remove some, but not all of that. Yes, for any arbitrary person it might be lifesaving, just like current methods. But at population scale it's not a panacea.