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The reason for having it in the first place was automatic detection of disk changes, instead of having to open a file manager and click on the A: logo as was the case with Windows (or typing A: in DOS), or using totally custom floppy mechanisms as was the case with the Mac.
I'm fairly sure almost all drives need the step command to update the status of their output pins, which are otherwise latched when nothing is happening. Most newer drives don't initiate any mechanical movement when the heads are at cylinder 0 and a step -1 command is issued, and so will remain silent in that situation while still updating their disk presence output. This behaviour is actually already present within the Amiga trackdisk.device, but is disabled by default because some older drives are too dumb to realise they shouldn't step backwards when they're at cylinder 0, so they force the head sled against its mechanical stop and risk misaligning the heads as a result. Instead, trackdisk.device defaults to stepping forward one cylinder, then back on the next click, so that the heads aren't forced against the stop. This is the safer option without knowing how old the mechanisms are which are attached.
The various "no click" programs can be used to change this option within trackdisk.device, letting you have click-free operation with most drives. But if you happen to have or connect a very old mechanism, such programs risk putting the heads out of alignment.
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05 February 2019, 10:02
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