Effective regulations very much do put the employer on the hook, no way to accept something like "voluntary employee risk-taking" outside of in some cases not looking for it as hard as they could. Employers are at risk of getting fined for tolerating (or worse) employee risk-taking and if those fines are sufficiently high they will certainly tell the employee "stop doing that that or else". And the last stage of "or else" certainly is getting fired, perfectly in line with other worker protection laws that might be in place that would otherwise prevent that getting fired.