I go through a lot of resumes, but hardcore job hopper resumes are still very rare. Numerically, they'd have to be overrepresented in the applicant pool due to changing jobs 2-5X more frequently than everyone else.
It's not a big deal if someone has a couple short jobs on their resume or even a series of short-term engagements. But what may not be obvious until you've done a lot of hiring is that it's really hard to tell the difference between someone who changes jobs every 12 months for a pay increase compared to someone who changes jobs every 12 months because they get PIPed and managed out of every company they work for. Some people are really good at interviewing, but will show up at your company and proceed to ride your performance management track until they're pushed out, at which case they hop into the next company and move on.
So at minimum, job hoppers get much more intensive interviews and reference checks. But more realistically I just give priority to candidates who have track records of accomplishing bigger things over longer periods of time at companies.
On top of that, most of our most productive engineers stayed over 4 years.
Unless you’re a senior or lead, it’s unlikely that you have had the opportunity to gain enough deep exposure to many technologies and problems in a very short tenure at a company.
Also I don't think seniors and leads with short stints are to be trusted (from recent experience with such people).
Staying after that in a lot of these cases mean a lack of interesting projects, and also end up with stagnation. My experience may be a bit affected by freelancing though :)