I'm not sure the exact answer but I imagine it is based on household income & length of credit history to go along with a good score. My parents scores are 800+ (not sure exact score but my mom's was 830 last time she pulled it & I'm sure my dad's is higher) But their length of credit I'm sure is at least 50 years or more.(assuming there were even CC back then)
Not sure about the 25K or 50K but they do have several CC that are over the 10K. They earn some great rewards that they pass along to me in the form of gift cards on occasion as they charge everything every month & then PIF when the bill comes.
Just to add to what was already said, Alliant nowadays gives up to 10k without income check (they don't even ask), and they will check for higher CL's. In former times, they gave more. Which means that, with higher income, you might be even better off with a different CU, which might start you with a higher limit.
My bank cc limits have crept up over time, but I don't have an account with any of those banks that traditionally offered high limits. Frex, WF got stuck at $8,900, although it doesn't really matter as its a Visa Signature card (but doesn't report as such).
Can you please explain your point.
In the past, household income and balance history would be the major factor in setting CLs. These days who knows. IMHO asking for a high CL unless its a business card is just drawing a big target on yourself. Along with revolving non-store CCs.