Caffeine is a mild stimulant and helps with focus, attention and endurance.
It's about as mild an energy boost you can get without significant side effects.
It's a diuretic for some people so in a survival situation it's use might lead to slightly accelerated dehydration but this depends on the individual
It's a morale booster as well.

It can also have barter/trade value as a commodity.
If you're packing some in your survival kit, the filters can be used to pre-filter brackish water before treatment.

I can quit coffee any time I want.
Besides, I only drink enough to make the headaches go away...