In order to maximize contributions, operational budgets must hit optimum efficiency at every layer of the organization. Most non-profits cannot offer the types of salaries and benefits comparable to huge corporations. As a result, the applicant pool is reduced and every applicant, from answering phones to directors, can be a rare gem.
Individuals who intentionally mean to do harm will seek out vulnerabilities and can penetrate deep into an organization, sometimes rising all the way to the top before they are discovered. Those who just need a second chance can be perceived as deceitful when criminal history is not brought to light early enough in employment. Are you worried about having to disqualify another applicant instead of working to mitige risk from a negligent hiring decision?