The Public Suffix List changes often. I have once worked with a team who built a major feature on top of PSL, but the person who built it did not at all consider how it might handle changes to it. Basically, the feature analyzed domains and uses PSL data to extract the "important part" of the domain, and then stored that in the database as part of a primary key in a table. But when the PSL changes, the database needed to be taken offline for certain tables to be completely rebuilt. And code querying the database had to be updated in lockstep with the database changes. This design made zero-downtime deployments difficult. It then took quite a while for the team to evolve the schema such that the database contents would not depend on the PSL.

This is just one cautionary tale I have personally experienced.