Thad Parker
My lathe has this feature. The on/off switch is built into the speed control lever. In order to be turned off, it must be returned to the slowest position. This prevents it from being at high speed when turned on.

It's a 1939 J.A. Faye & Egan model 400

I turn on my FIL's pm 3520b a few times a year, and returning to my lathe, the only thing I miss from the pm is the digital speed readout. I don't feel inconvenienced by this safety feature.

~ Thad