You can tell from the go the capital waistland is not as developed as the west coast, fallout 2 which is before fallout 3 has fully functioning cities built from scratch, all the settlements build from scratch in fallout 3 dont really seem that big or advanced. If you looked at the amount of bottle caps in the DC area compared to the amount chips in the whole of vegas i think you would find vegas would have a very low value currency if the did use chips. Hundreds of thousands of chips, if not millions, are in each casino, in a adverage store you would maybe have a few hundred caps and in the waistland most would have been lost while the chips would be in the casino's own private vaults. Bottlecaps where dropped by the NCR for a reason, once certain machines could be made of repaired they could be forged and due to their age fakes couldnt be easily seen (plus theyre not worth much). It would be nice to see chips u can use only in the casino u brought them from, like in real life, however as a city wide currency they would just be too easy to forge in the fallout world, plus casino's wouldnt really accept other casino's chips...
1. There are also millions of caps, as evidenced by the BoS's reserves. There are also some items worth less than a cap, that you had to pay extra for. Chips, if they even had a lower value, would make transactions easier, especially due to denominations like 50's, 100s and 300's
2. Every chip was meant to be redeemable for dollars, so casinos could recognize each others coins, especially if the original currency was burned away. The value should be same even if the colors aren't
3. Bottlecaps would be easier to forge than chips, which were specifically designed to stop counterfeiters and cheaters. A bottlecap is just formed aluminum with a design, poker chips are high-quality plastic/metal products. Although a counterfeiting quest could be added, this is not a serious concern.
4. I think it would make sense for currency exhanges to exist, if only for travelers to boost the local economy (depending on prevalence, I'm thinking 10-1 for chips or maybe some variance if the economy is booming or busting) Take a look at the "realistic economies page for more.