Why do some keep searching for the coffee with the highest caffeine content?

All Arabica beans have the same amount of caffeine, varying only slightly on the plant it's harvested from.

If it's a light roast, it will technically have more caffeine than a dark roast of the same bean, but the difference will not be perceivable unless you're using green beans... but that doesn't agree with my taste.

Robusto beans have a higher caffeine content, however they lack the flavor of the higher quality Arabica.

So if you're looking for more caffeine, either go for the Robusto or else use more coffee when you brew. Both these routes will lead to a degradation in flavor maximization, but that's your choice. I won't go into your house and tell you how to brew your coffee.

I don't think we drink coffee for the caffeine. We drink coffee because it smells and tastes amazing.

I definitely drink coffee/tea for the same reason I drink beer - I love the taste. I don't care much about being drunk, or strung out on caffeine. I'm also a bit of a coffee snob as I typically drink my coffee black, and cringe at people who add loads of cream and sugar. And with coffee, the smell is amazing.

Like alcohol, caffeine is also a drug, and people abuse drugs. Some people really like extra focus and energy caffeine grants them, and more they use, the more they need to get the same effect due to tolerance build up. On the same token, the more used, the worst the withdrawal symptoms are. I know someone who needs at least 3 cups of coffee in the morning to avoid getting jitters and a killer headache. She also used copious amounts of cream and sugar. That person would probably want to seek out stronger coffee, and wouldn't mind taste degradation as they would be drowning it in cream and sugar.

I will admit to drinking my Americano with extra shots of espresso on those especially sleep-deprived days, I will also drink 3 cups of coffee per day because I really like the taste of black coffee. However, I can also go every morning without caffeine and not suffer from withdrawal. It's a mix of pleasure and utility, but mostly pleasure.