Virtually, every modern DRO comes with some flavor of a persistent tool offset memory that lets the user enter offsets for some commonly used tools and recall them as needed. An obvious prerequisite for this feature is the use of indexable tool holders and/or insert tooling, or the offsets will change each time the cutter is re-inserted. In the past, few small shops could afford such tooling. These days, the situation is much better thanks to the availability of inexpensive import insert tooling, end mill holders, and quick change lathe tool posts. As such, the ability to quickly swap tools without needing to re-indicate the surface can be very appealing. Unfortunately, the implementation of saved tool offset memory is outright horrid on most traditional Digital Readouts. Entering and recalling tool offsets involves a complicated sequence of button presses, and at the end, you still need to have a cheat sheet to remember what tool each memory slot holds.
