Grammar is that part of language learning that everybody loves to hate. A lot of new-fangled language learning systems like to pretend they won’t even teach you any grammar at all – things sell better that way.
There are lots of problems with this. For one thing, we tend to think that all of the meaning to be found in language is in its words, and the grammar is just the fiddly useless stuff that gives us headaches. But actually grammar has tremendous communicative value. Languages like Russian and Greek, with more flexible word orders than English, play with syntax to emphasize parts of a sentence. Some languages, classical Greek for instance, have different verb tenses for things that happened in the past, things that happened in the past and may or may not be continuing today, things that happened in the past and totally stopped happening before I said this…etc. Many languages have different pronoun forms and different verb conjugations for dual (i.e. specifically two people) as opposed to the plural (more than two), which I imagine makes love letters and friendly quarrels much more intimate.
These are just examples I can think of off the top of my head. And then there’s the simple fact that grammar does exist, and it is used by the language’s speakers, meaning that if you ever hope to be able to listen to or read something in the language with any real comprehension, you’re going to have to know this stuff. And also meaning that if you ever want to stop sounding like a perpetual novice, you’re going to have learn to use the grammar correctly.
I think the problem boils down to the fact that people tend to conflate the category of “learning grammar in a foreign language” with two experiences:
1. the pain of rote memorization, and
2. the inefficiency of meaningless learning.
Rote memorization is, unfortunately, how most grammar is taught in most contexts. If you ever chanted all 27,000 forms of a verb conjugation or noun declension, you know what I’m talking about. Personally, I sometimes find this kind of activity kind of pleasant, but in a mind-numbing way :) No, it’s not a good way to learn.
Meaningless learning is closely related. Various grammatical forms floating freely in space, with no meaning or context attached to them, are very hard to acquire. The consensus among second language acquisition researchers is that there has to be some meaning, some way for us to subsume the form into our memories, for any of that information to ever stick. Unfortunately, grammar is not often taught in a meaningful way, which means that “studying grammar” becomes equated for most people with the sensation of bashing one’s forehead into a brick wall.
Poor grammar! Don’t blame grammar! This pain and frustration is not a necessary part of studying grammar. And grammar itself is an essential part of language; if vocabulary is the bricks, grammar is the mortar. We need the mortar if we’re going to build this monument!