Viroids are opportunistic infections, generally need the right or even ideal conditions to spread and establish their infection, and small time tent growers growing from seeds (most of what we see on AFN) don't have these risk factors.
I presume viroids are very serious ongoing problems for the legal commercial grows. These seem to be where all the hype is centered. These presumably have essentially perfect conditions for viroid spread within the facility, including using mother plants, cuttings, cloning, etc., facility-wide interconnected and likely even recycled water supplies, have poor sanitation/hygiene, workers don't wear clean disposable (or freshly washed) outer clothing, they likely don't test and don't really want to know if their crops are infected (the CEO, investors, consumers, regulators, etc. might get upset), etc.