Migrations
Big Companies have lots of software. The Software industry moves pretty fast. However, not all pieces of software are moving that fast. There are always competing priorities between news business domains, acquisitions, new features, improving user experience, fixing bugs, improving security, and being up to date. If you have good architecture, isolation of databases, proper contracts, and tests, migrations can be much easier. However, not all pieces of software have the same conditions as you might have orphan software with no owners, old tech, lack of testing, lack of isolation; in those conditions, migrations could be pretty challenging. There will always have migrations one way or another. In the last decade, lots of companies have been migrating from on-premises to the Cloud.