This:
https://hackerlife.co/blog/san-francisco-large-corporation-e...Suggests median tenures at small tech companies can be as low as 1.5years.
For me - it depends on the stage of career a candidate is at.
If you're not job hopping every 2-3 years in the early stages of your career (say, first 8-10 years out of school), you're without doubt losing out monetarily (which may indicate a lack of ambition).
On the other hand, if you've not managed to hold down a job for over two years (or any job for over 18 months), you ring bells in my head of maybe just having managed to not get let go for lack of performance and bailing out before it makes it to your record.
Those are both offset of some of your roles are listed as contracts (but rest assured I'll be getting your references or LinkedIn or network-sourced ex-colleagues checked to make sure they don't describe them as permanent full time roles).