Why ask?
To further solidify the notion that you, as a recruitee, must show total devotion and unwavering loyalty to a potential employer.
Obviously recruiters know that people jump around after contracts or when they feel they are not being paid enough, that people scatter shot apply to anything like guys swiping on tinder because their prior experience trying to get a job has shown them that there's really no rhyme or reason to it, that desired qualifications are nearly always absurdly niche or dramatically overinflated, and that there's a hundred or a thousand people applying to every job opening.
It is literally their job to facilitate this process. Of course they know how all if this works.
This rhetoric is basically an attempt at conditioning you into being servile. If you 'play ball', you might get this particular job, and then they'll basically lie to you about upward mobility, job stability or repeating contracts.
They are salesman. They sell the job to you and you to the company.
Why would they be anything other than slimy underhanded liars?