(1) likelihood of repayment & ease of collection; and
(2) net-profitability of a customer, after all fees, charge-reversals, support-costs, etc are considered.
You're under the hypnotic sway of a legal fiction – "community property" – that paints an attractive, childlike simplicity over the situation that doesn't exist in reality.
On the other hand, credit companies have real data about repayment rates, collection yield, & lifetime profitability.
And even with the strongest possible community property laws, in the event of disputes (& divorces!), there's no magic wand a creditor can wave to costlessly collect from DHH if JHH defaults, or vice-versa.
Even if the creditor is completely in-the-right, essentially, all they can do is send threatening letters & make adverse credit reports – which will have differential effectiveness against individuals despite any legal fiat claiming they're the same financial unit.
And whether DHH would be on the hook for JHH's debts is murky & jurisdiction-dependent. Only some US states use "community property" rules to make spouses jointly responsible for each others' debt – and notably, Illinois (where DHH's partnership/CTO position in 37signals is based) isn't one of them. (See: <https://www.nolo.com/legal-encyclopedia/am-i-liable-my-spous...)
Some reports also place DHH's residence in Spain – and according to <http://www.coupleseurope.eu/en/spain/topics/2-is-there-a-sta..., there, "each spouse… is not responsible for the debts of the other".
So what's the legal or statistical basis for your implication that "community property" makes them identical credit- and profitability- risks? (Has the couple even revealed that they're in a "community property" jurisdiction?)