Hulu has DRM issues in Firefox and their DRM just fails with unknown errors on about ~15% of content they host (anecdotally, of course, I have no specific data). There's no way for me to tell if a specific episode of a show will fail or not, some succeed, others don't. I at least find no pattern for this. From this perspective, they are essentially randomly breaking 100% of Firefox users some seemingly random percentage of the time.
They have "good" business reasons to require this DRM and whatever this random broken user percentage is, I'm sure it meets their bottom-line criteria as a business.
"95%" uptime for Chrome users is only "one-9", but it's still got that one 9. That's an acceptable SLA to many businesses. A business might easily decide attestation is worth that "uptime risk" because it sells more ads or makes the DRM vendors happier (and thus the content owners are happier) or any other number of "good" business reasons.