Because there's nothing stopping them spinning.
It means done without ceasing, without stopping; continuously.
The current Guinness World Record for the longest time jumping rope without stopping is 30 hours and 40 minutes.
stopping
Without stopping to think, he pulled the dog away from the oncoming car.
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The word nonstop can be an adjective and an adverb. It means without stopping.
sneeaae
Cardiac
25
Stopping it dead -in other words, stopping it without allowing it to run down.
10000km