Because I never encountered AI which tried to give me a loan, so I am sure that it simply doesn't know how to use this feature. And if he doesn't trying to give me a loan, than it means that he never trying to do this with other Ai countries. How it was possible to make loans available for Ai in EU2? Also, I am bringing this point up because I don't want to purchase a game, in which Ai doesn't know how to use all of it's features.
IMO the lack of this feature hardly have a decisive impact on gameplay. I think loan-giving is primarily intended for MP - I remember earning lots of money by this schemes in earlier EU2 in SP...
There are much more important tactical AI issues that have been solved. Now Ai doesn't overstack his troops, it does't lift all sieges once you besiege his capital, it tries to accumulate troops before attack... In my game OE cased a lots of proglems when they besieged Napoli - they somehow were sneaking past my ships and landed lots of troops there, and maneuvered rather skillfully (especially compared to EU2 Ai).
Though I admit I was a bit careless about this war and thought: I have better techs, more ships, and whether AI has 10k or 40k doesn't make difference... It does, actually. And I think my overstretched empire is going to collapse soon, because I was taking many things for granted (I am Spain, Hard/Weakling settings).
Though *call to arms allies-> ally refuse and leave an alliance-> join again a day thereafter* issue is still there. And Genoa in my game has 49k stack of troops... (I don't complain as I attribute that to difficulty setting and regard it as a "balance" thing).