I think it's just how you're valuing resources down the road.
Assuming an average game (which means we're looking at the results when you play an arbitrarily large amount of Arkham Horror, tending towards infinity, and not just the bias of looking at 3 or even 12 games), a few things happen in general:
1. Your investigator board gets filled. You have the cards you need and/or can play at the moment that are doing a sufficient job.
2. Because of that, you tend towards resource glut in the late game. You gain a resource every turn, but do not always have things to spend them on.
3. Resources are more replaceable than cards. You gain a card and a resource each turn, but "mana" in this game is "colorless". Your resources can pay for any of your cards. You also gain a card every turn, but cards do unique things while in your hand that resources do not while in your pool. Spending a small bonus of resources for a gain is therefore less committing than using a card in your hand, because you'll get more resources, all things being equal. You will not get that card back (yes, you could shuffle through your whole deck, lose a Sanity, and eventually draw into it again, but that requires such a huge scenario that we'll have to see if they design for things to be that long).
4. For what it's worth, you have a maximum amount of cards (8), but not resources, which also pushes up the importance of cards vs. resources in a minor way.
You can avoid these things in part by having, say, an Event-heavy deck that can always use its resources every turn, but even then, in the long run, you tend to be card-shy and resource-heavy in the late game. You've invested your cards for their unique abilities, and have a pool of indistinguishable resources.
Now we need to look at what difficulties we're facing. For the default adventure, under Standard difficulty, and ignoring iconography (because we kind of have to), the average draw from Ye Olde Chaos Bag is -1 (obviously, adjust this metric when you're playing with a different bag). That means on any given test, you can look at the difficulty, look at your character skills, and subtract 1 from them to see what your average draw will result in.
So for the first campaign, a 1 resource investment on a Skill Talent will negate the expected result of the Chaos Bag...and that's resuable every turn. That's excellent value for the dollar.
Furthermore, the best you can do from the Chaos Bag on Standard is +1 (disallowing weird Elder Sign draws for some characters). That means a 2 resource spend on your chosen Skill Talent will not only negate the standard penalty of the Chaos Bag, it will turn your average draw into the best possible draw it could be. That means if your Location or Agenda has a particular test that you have to pass, and things are looking grim, with an appropriate Skill Talent out, you could take two actions to gain 2 resources and then you will do as best as you possibly can, on average, on that vital test. Every turn.
If you're rolling in the dough, you can spend more to avoid the -4s and -3s, but effectively those are like drawing the Tentacle -- a loss that probably is not worth mitigating on an average budget.
Now, this thought experiment is simplifying a bunch of stuff. For instance, if you have a 2 Skill in something, and you need a 4 to get through a nasty Agenda requirement, you're looking at spending at least 3 resources to negate the effect of the Chaos Bag as best you reasonably can. We're just looking at a default situation of trying to get your Skill draws to parity vs. the bag.
But the net result is: resources are more expendable and less unique than cards. You tend towards resource glut in the long game. Not every card drawn has an icon that is useful to commit to every possible test, but with a Skill Talent out, you can reliably smooth out the bad distribution in the Chaos Bag for important tests. By and large, you don't need to negate the -3s and -4s with a huge resource spend; they're typically the same as drawing the Tentacle, but the option is there for truly game-saving draws. And, finally, Talents don't take up character slots, so you can develop the rest of your board without having to consider Hard Knocks or Baseball Bat, say.
They're very efficient ways to make your average draw smoother, along with an oh-**** panic button mode that lets you turn a huge resource glut into a ludicrously high bonus, and as such I'm a big fan of them.