Differences in the rate of absorption can definitely be important to addiction; oral amphetamines are not particularly addictive, but amphetamines taken in other ways that increase absorption rate are very addictive. And the last I checked the research on that, there wasn't much understanding of exactly why the line there is where it is. Perhaps alcohol just works completely differently, but it is also possible that drinking on an empty stomach, or drinking carbonated drinks, doesn't increase absorption enough to make a difference. Or perhaps it does make a difference, but not enough to have turned up in any research yet; this isn't an area where small effects would be easy to detect.