The real fun starts when you have to do an unscheduled renewal!

Companies are generally able to develop a workable process around regularly-scheduled tasks. If you can't, you'll quickly run into trouble due to late salary payouts or missed tax filing deadlines. They'll rapidly accumulate a thick layer of bureaucracy around it, but as long as it gets exercised regularly it'll remain more-or-less functional.

Try the same with PKI and you'll run into massive issues during mass revocation events. Having a renewal process which takes 2 months and involves dozens of stakeholders is totally fine for a cert which gets renewed every 12 months on a well-known date - but not when you're working with a 72-hour deadline...