From what I've read, hops is what gives beer its bitter taste. But why are the more expensive craft beers so INCREDIBLY bitter tasting to me? Is it something people get used to and they don't taste the bitterness after awhile, or does it taste bitter to them too, but they actually like the bitter taste? Thanks
You're exactly right.
Hops are used for three reasons: They provide bitterness, flavor, and aroma to the beer.
Since most craft brewers are trying to get the most possible flavor, they use extremely large amounts of hops. In most cases, that increases the bitterness as well as the flavor. You're right that many people simply get used to this level of bitterness, and can even come to prefer it.
There are ways for brewers to increase the flavor and aroma without such a huge increase in bitterness, but just between us, some brewers either don't understand it all that well, or sometimes feel they need the extra high bitterness just because other breweries have it.
Bottom line: just try a wide variety and then you'll know which breweries you prefer.