When a business team keeps using their own spreadsheet after a reporting platform ships, the stated reason is usually that the numbers are wrong. Investigated, the numbers are typically not wrong — they are defined differently. Somebody chose a definition of active customer or recognised revenue or open incident that is defensible and is not the one the business team has used for years, and nobody reconciled the two or told anyone it had changed.
That is a governance and ownership problem wearing a technical costume, and it is fatal, because trust in a data product is lost quickly and regained slowly. Once a team has found one number they believe is wrong, they revert to their own source and the platform becomes an expensive parallel system.
The second failure is ownership. Data products get built by a central team and handed to nobody. When source systems change — and they change constantly — the pipeline breaks or, worse, silently degrades, and the first person to notice is a business user who now trusts the platform less. Data quality is not a one-off remediation project; it is an ownership model, and if no name is attached to a dataset it will decay regardless of the tooling around it.