Physics is why it takes a while when simply setting the correct pressure and letting the CO2 dissolve (and probably some chemistry, but neither is my strong suit). I am not aware of any hard study that was done in the brewing community to figure out the exact point where equilibrium is achieved. My kegs may actually be carbonated within a week or so, at least to a drinkable point, but because I have kegs in the pipeline I don't even check them until the two or three week point, and often later than that. Besides, waiting a few weeks allows the beer to condition a bit more. If I need a keg to carbonate more quickly, I will hook it up to 30psi in my keezer for about 24 hours, then bleed it off and hook it to the lower pressure to finish. This seems to get good results within a few days to about a week.
My guess as to why nobody has put out a chart that includes the necessary time frame would have to do with the endless array of variables that may come into play. I would assume the shape of the keg and the surface area the specific shape creates would influence the speed that the beer carbonates. The temp/vol relationship comes into play as well. A keg at 60 degrees & 23psi will carbonate more slowly than one that is at 36 degrees & 10psi - though the volume of CO2 that is dissolved is the same. I am sure the volume of beer being carbonated would also come into play. What the chart allows me to do is know that for as long as I have the keg at the proper temperature & the CO2 to the correct psi, I will not have over carbonated beer.
I am sure the amount of time it takes to carbonate for a fixed set of rules (5 gallons of beer at 35 degrees, 2.4 vols, standard ball lock corney keg) could be calculated, and probably has been more than once, by somebody with more of a physics/chemistry background that I have (and the desire to do it), but is it really necessary? The keg will be carbed when it is carbed (similar to bottle carbonation, but without the complications of a natural fermentation generating the CO2). If it takes an extra day or two it probably isn't a big deal, especially once a pipeline has been established. There are many things that this hobby has taught me, but probably the two biggest things have been patience and longer range planning. In nearly everything I do I am a "wait until the last minute" person, but I know that if I need to have a beer ready to be served on a specific date, I need to plan on having it ready at least a week in advance or maybe even more just in case.