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I don't have to turn my blinkers or windshield wipers on before I use them but in every car I've ever been in with cruise control, you have to turn it on before you set the cruising speed.
Why should I ever turn cruise control off? Is there a problem with leaving it on all the time and just setting my cruising speed at any time without first having to turn it on?
If there is a technical problem caused by leaving cruise control on, why haven't we solved it? I can tweet from a refrigerator but it seems we just haven't wanted to solve this problem for some reason.