The Amish did not choose to "stay" in any given time. Instead, when a new technology comes along they ask questions about how it will affect their community, tradition of self sufficiency, and values.

For example, you might be surprised to learn many Amish communities have a telephone or two, but they do not belong to anyone. Instead, they'll be in a booth shared by many families, and used by necessity only. If they had phones in their homes, they might be inclined to call their neighbor up the road to check how the new baby is doing, instead of visit in person, or spend their time socializing on the phone instead of spending time with their family.

The story is similar for the technological conveniences present in many Amish communities. Diesel generators, solar panels, lead-acid batteries, and pneumatic tools are all regularly found, but they pay close attention to how they use them and their affects. You might have electricity (off grid, naturally) in your store to power cash registers and lights, but still use oil lamps in the home. At work, it enables your livelihood, but at home it's an unnecessary distraction.

For a much more eloquent explanation, see here: https://groups.etown.edu/amishstudies/cultural-practices/technology/

For further reading I highly recommend The Amish by Donald B. Kraybill, Karen M. Johnson-Weiner, and Steven M. Nolt (cited in the above). It's a fascinating read, it debunks most of the myths around the Amish way of life and does a good job of explaining their processes and traditions.

This is my first post on /r/AskHistorians after many years of reading. This is a topic that fascinates me but I have no formal education in Amish Studies. I hope it's up to snuff, mods please let me know if it's not!