1️⃣ Shays were built for low‑speed, temporary mining & logging lines
“These are not the type you see in Utah … built for rough (sometimes temporary) track and steep inclines. Often used in mining and logging.” — codazoda
2️⃣ Surviving units are of interest and located at specific heritage sites
“Shays were very well suited to low‑speed operation on dirt‑cheap (often temporary) tracks … narrow‑gauge, light rail & iffy roadbed, tight curves, and steep grades.” — bell‑cot
Examples: Cass Scenic Railroad (USA), Duncan BC museum (Canada), Newnes railway line (Australia).
3️⃣ Mechanical quirks and nostalgic memories of the design
“The most significant design difference between Shays and Heislers was the arrangement of the driving cylinders. The Shays had either two or three driving cylinders mounted on the right hand side of the locomotive… In the Heislers, the driving cylinders were located in the middle of the locomotive.” — jorgen123
(Also recalled by model‑railroading fans like dhosek who remembered 1970s kit‑bashing articles.)