I agree that how much water you carry depends on your travel plans and outside sources. In hot, arid climates 2 gallons might not be enough, given driver and passengers for two days. (When I stock emergency supplies in my vehicle, I plan to reasonably accommodate my passengers as well as myself.)

But most parts of the country I've visited outside the southwest, groundwater is never far enough away to be a concern. As long as I have ways to make it safe to drink, a reasonable starter supply seems more appropriate. Less space and safety concerns, and space is always an issue in my vehicles.

Not trying to convince anyone, just explaining myself (probably needlessly).

Also, in my experience there are no reliability issues using the new, thin containers used in disposable bottles of water. I think that Poland Spring was the first to reduce their plastic content, and I use that brand almost exclusively (please don't tell me nasty things about them, I like the taste). I have had both opened and unopened bottles of this type in my Jeep for months without ill effect, through this summer's record high temperatures (over 100*F for a week, a record in NJ) and multiple freeze/thaw cycles in the Winter. I've even refilled and reused them for weeks. I wouldn't trust the milky, translucent containers in extreme temperatures, but I have some in storage at home that are over a year old.