It's hard to invent logic supporting the fitment of more than two auxiliary lights if your vehicle doesn't occasionally find itself bounding across reasonably open terrain at very high speeds, or being used for long durations in arctic climates.
Some vehicles are fitted with many lights because lights can be broken, and it's always best to have backup systems.
Numerous lights are also fitted to vehicles driven at very high speeds, as such a vehicle requires several lights to appropriately illuminate the entire length of the driver's chosen path.
Certain base vehicles (or any primary vehicle used in complex vehicle-based expeditions) may be fitted with a number of light sources simply to illuminate a camp or working area.
Another reason is sometimes misunderstood.
Some vehicles experience long duration use in deceptively treacherous conditions, such as those found in arctic environments with lengthy darkened periods. There, multiple light sources can be used to illuminate an area to be traveled from several angles at once, even at very low speeds.
This can be the difference between an entirely unexpected and potentially fatal total vehicular loss and a trouble-free journey.
Those are the primary reasons to invest in complex lighting systems. There's nothing stopping someone from buying something they want, though. One doesn't need a reason beyond desire to own such lights.
As for electrical charging and storage systems, the proper advise has been given.
This is not the most accurate analogy, but the hose is the problem; not the bucket. A new or uprated alternator is a good starting point.
Once you sort that out, it's time to consider capacity. Big, fat batteries and parallel connections tend to reign supreme, but they are pointless (aside from an occasional long draw) if your alternator can never adequately supply your electrical needs.
After that, you can learn through experience whether or not you require a secondary, isolated, battery system. This is not a patch to sort out a weak charging system, it is an expensive and reasonably complex decision.
As usual, however, if you want a battery that just fucking
works, all the time, every time:
http://buy.northstarbattery.com/
You knew it was coming eventually...
Cheers,
Kennith