Many plants in North America and elsewhere were built in the past century. For example, the ExxonMobil plant in Joliet, Illinois, is currently the youngest oil refinery in the United States — and it was built in the early 1980s. You may work in a plant that is well past its original life expectancy, but you have somehow kept it working all these years.
Some process plants have done partial DCS upgrades, but others — maybe even yours — are still operating with large parts of the original control system still in operation. You may have patched it, upgraded it and coddled it along, but it may be well past its prime.
Worse yet, your control system wasn’t designed for the plant you have today — it was created specifically for the plant that was built long ago. Think of all the changes that have been made in that time, all the improvements in quality, throughput and enterprise integration you’ve made — or would like to make — if only the control system would let you.