why do you need to carry tools in the car?
Because most of the time if something goes wrong it can be easily fixed in a few minutes with a few simple tools: things like giving the MAF sensor a clean, replacing a bit of wiring, wiring/bolting back on something that's dropped off, and so on. These are all things that have happened to cars I've been travelling with over the last few years.
On my own car for example I reversed a bit too enthusiastically in a hotel car park in Suffolk and caught the rear of the exhaust on a low curb. Not enough to damage the exhaust, but it tore the rubber mountings and the exhaust was dragging perilously close to the ground. 5 minutes with a couple of jubilee clips and it was sorted.
The alternative of waiting an hour or two for the rescue service to turn up is a bit of a pain compared to getting stuck in and sorting it yourself.
