Business systems: inventory, sales orders, purchasing, forecasting, accounting, etc.

One is one of the largest master distributors of industrial supplies in the world.

Another is a web-based and catalog distributor of consumer goods (mostly apparel.)

Each has acquired 5 competitors in the past 10 years, converting all of them from whatever they were running to their 20+ year old software written in 40+ year old technology. Both were super agile long before any of us ever used the term.

(All client side web software is written in javascript. Some things do change.)