In fact, because of weak internal plastic parts wear, it is better NOT to move the ON-OFF switch (Left-Right) too often. I have seen the internals and now understand some of the switches failures with age.
P.S.: by the way, as documented in Owner's manual the Cruise-Control will not engage below 25 MPH (40 Km/h) so there is no danger of such incident even if you accidently touch the SET or RES button at very low speed (or while stopped).
I don't see any reason to turn it off.
I think it may be there for an emergency shut-off, if something gets out of control and there no other way to turn it off.
I use it sometimes only when cleaning bike and putting armor-all on the black plastic.
For years cars had cruiser control without an on/off switch. I drove many miles in those cars with no issues. I say leave it on and don't worry. Even if you accidently engage the cruise at some point the brakes will override it, so no worries.
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