Elsewhere, on another site, I read this. It was talking about that other site (which is a no-subscription-required site, like IMAO). Seemed to make sense.

A web site that depends on 100% voluntary donations [or no donations at all] has much more flexibility than a web site that requires a mandatory payment.

Such a site has very limited legal liability.

If a monthly subscription is required, the site is instantly vulnerable to:
copyright lawsuits [because they’re making money off others’ work]
libel lawsuits, and
hate speech lawsuits that result in injury or damage.

Lawyers. God love ’em.