I went through some headphones and headphone amps and the 32ohm are most common across everything, so it seems.
The 180, 250...volume dropped noticeably on some amps, but some interface headphone amps handle them just fine.
I never got up to the 600 ohm which audiophiles love.
The difference between amps is interesting and like so many things some cheap ones sound as good as expensive ones to my ears. Maybe I dont have "golden ears" but there is a limit to ROI when spending doesnt seem to offer an equal increase in what Im hearing.
When recording a band the Behringer Multi-Headphone amp worked well and was like $50 for 4qty headphone amp.
I take the word from others who do pro stuff and add that into the gear purchases too (maybe they have golden ears they at l;east have golden records)....
I grabbed the Bob Ludwig headphone amp of Grace Designs first release 901 (and surprisingly kept it,) and settled on 880 250ohm Beyers because a lot of people in the biz seemed to say they are good, flat, etc.. But with my ears my interface headphone amp, which can take up to 600ohm, sounds about as good as the GD headphone amp. Comparing Behringer Multi, MOTU and a couple other amps and it wasnt night and day, imo.. However the GD 901 can handle ALL headphones and its a DAC and built like a tank, so it offers confidence of listening pleasure when testing out any type headphone.
Now getting into headphones thats where I heard a much bigger sound differences. Closed backs, open backs, brand name designs etc....some cheap Takstar 670? were a huge sound and fun for Symphony listening bliss of wide dynamic ranges where unlike a lot of pop music everything is sqaushed to some loudness radio quality, and maybe high quality isnt needed as much; so the headphones can be the largest difference imo.
Sony, Beyer, Seinheiser, Beyers...$60 to $200 ish was all I test drove. Its subjective which a person prefers, as in speakers.
A lot of the headphones are 250-600ohm so you need a better built headphone amp to even test drive them correctly. So thats a reason for having a better built headphone amp, as these amps allow all variations of impedance.
For doing HR recording and closed back, tracking, ...then low ohms rule and can be ran easily by interfaces designed with 32ohm.
Im not sure how that historical decision was made or why? Maybe its more expensive to make a amp that drives 600 ohms?
I dont know but 32ohm headphones seem to work in everything.