LNT is lawyer science, low dose radiation risk (cancer induction) is stochastic. There is already a high prevalence of cancer in society. To protect against possible litigation we eliminate sources as a possible induction points.
However, iff you developed a radiation induced cancer there's very little way to determine if your (mulitple) DNA errors were induced by cosmic rays or that time you walked past a bucket of naturally occurring radiation or due to those flights you took from Colorado to Brazil.
The dose makes the poison, we protect (and waste inordinate amounts of time and money) against low levels -- because we're ignorant to the precise pathways of cancer induction.
And not court of law, by evidence and observation, i.e. science.