Some purists insist that they role dice, so we just let 'em and the resulting game feels quite like you're using gambler's dice.
I'm not sure that factors into the game (have played but its been a while). Cards seem like a more controlled way to distribute the results with some randomness.
only one way to get a 12 (6+6) but 7 much more likely.. (6+1, 5+2, 4+3, 3+4, 2+5, 1+6)
as someone who played a bit of online backgammon back in the day, We always suspected the random dice rolls behaved differently in the game than playing in real life...
They basically made one card for each possiblity of pair of dices, so there is a 7 card for 6+1, another for 5+2, and so on...
Playing with it is MUCH better than with dice... when I played with the dice that came with my copy with catan, the dice were clearly defective (rolls weren't just random-looking, they were WILDLY wrong, it rolled 10s 2 times the amount of 7s...), and the game was super boring, it would end with everyone having the same materials and not having others, so not even trade would fix the game, we had stuff like 10 turns in a row where noone had one particular item while the 'bank' ran out of the other items because everyone had lots of them.
So the game pace slowed to a crawl... Also, the funky dice never rolling bricks meant people would quickly rack up random resources, sometimes like 3 of each, so they ended with 9 cards, and would then lose to robber rolls (7).
Then of course in one game where this happened there was an asshole cousin that thought it would be hilarious to hog resources and make the game worse, he would spend his whole turn making 'negotiations' with everyone, and them cancelling them, wasting like 5 minutes every time it was his turn, and sometimes if 7 was taking long enough have 20 cards on his hand...
We don't play with that cousin anymore either.
But yeah, not having a way to build roads make the game suuuuuper slow.
An interesting bit of trivia: In roman times it seems they played with 3 dice instead of 2: http://www.bkgm.com/variants/Tabula.html
Likewise, if you use the Traders and Barbarians dice-deck, the same thing applies - there are 5X as many 6s and 8s in the deck as there are 2s and 12s.
http://www.catan.com/files/styles/lightboxy/public/gallery/d...
Notice that the 12 has one dot, the 9 (6+3, 5+4, 4+5, 3+6) has 4 dots, and the 3 (2+1, 1+2) has 2 dots. The gray robber piece is sitting on a red number token, which is either a 6 or an 8 and has 5 dots because it is more likely to be rolled.
In the game, you develop your pieces with the hopes of getting resources based on the adjacent numbers being rolled. It definitely creates a lot of stress in some people when "eights are being rolled all the time this game but never sixes!" or "your stupid 10 keeps getting rolled when it shouldn't, that's not fair!"
I think I'll give it a try tonight with some numbered cards. I just threw some together in Excel: 1-6 in B1-G1, 1-6 in A2-A7, and the formula
=B$1&" + "&$A2&" = "&(B$1+$A2)
spread across the grid and printed that out, but on doing a little, ah, market research, it looks like you can buy official Catan decks like this at https://boardgamegeek.com/boardgameexpansion/20038/catan-eve.... Or download this: https://boardgamegeek.com/filepage/40420/deck-dice-separate-... (note: not the above). Or someone else pointed out that you can simulate it with two matching decks of cards with: one 2
two 3S
three 4S
four 5S
five 6S
six 7S
five 8S
four 9S
three 10S
two Jacks
one Queen
Other market research says that people start counting cards to see when their numbers are going to come up again....perhaps some compromise, with perhaps two or three such decks? Real dice are an approximation of an infinite number of shuffled decks of dice, and I imagine you'd go through on the order of 100 'cards' in a given game, so with more than 3 or 4 decks you could end up with certain cards/numbers that never appeared, which seems to happen frequently and cause ire in games with real dice...interesting. Science is required! Sorry for rambling/thinking out loud.