Well I'll have you know that despite having assembled all my bikes with multitools (except obvious major operations like BB installation, pressing in headset cups to frame, etc), my bolts never come loose. The only emergencies I have are when parts actually break or cease functioning...like brake adjustment due to wear or wheel repositioning due to chain stretch or some other unpredictable failure (such as, for example, when I had to rearrange my chainring bolts, on the side of the road, in the snow, because the threads on some of the bolts eroded because I moved my chainring to the inside of the crank spider and didn't realized I should have also faced the bolts inwards so the chainring would bear on the smooth shoulders of the bolts instead of the threads). So if your emergencies are that bolts are just coming loose for no reason, then I submit there is something wrong with your assembly technique.

Other than that a single ride isn't enough time to fine tune a bike's fit...that takes many hundreds of miles and the adjustments need to be made immediately before the last perfect millimeter of adjustment is forgotten.

P.S. Or for another perfect example of an unpredictable emergency: One time I let an LBS change my flat tire and didn't discover that they totally discombobulated my gear adjustment until I was several miles away...so yeah I needed the multitool to fix the mistakes of those clueless LBS mechanics. This is the same LBS who lectured me for clicking through my gears in the store because "you'll break your shifter if you shift while not pedalling"...no, LBS man, YOU are the one that's going to break my bike because you haven't even the slightest idea what you're talking about!