Yeah, but it does that badly, that's the problem. It has a potential NNT of 100, which is a high number for such a common disease (in the case of a NNT of 36 in a perfect case, it's not that bad though).

The high NNT also means that it is less likely to achieve any kind of herd protection. Compared to for example the measles vaccine with a NNT of ~7, a 100 seems quite high (disclosure: but this is actually a tricky comparison and may not be fair for the flu vaccine. The NNT is heavily influenced by the baseline risk of actually getting the disease. If the baseline risk is very high to get sick in the first place, which is often the case for classic childhood disease like measles or varicella, the NNT is usually much lower even with a less effective vaccine. The NNT for the HPV vaccine against cervical cancer is somewhere in the range of 5000-8000 because of the low baseline risk of getting the disease).

Furthermore, even the wikipedia article (which I object somewhat to) agrees on the fact, that for at least for the elderly, it's not very effective:

The group most vulnerable to non-pandemic flu, the elderly, is also the least to benefit from the vaccine.

which probably isn't to blame on the vaccine alone, but also on the less robust immunologic response of the elderly.

And citing from the Cochrane review:

In children under the age of two the data are extremely limited, but vaccination appeared to confer no measurable benefit.

In the end, these results are most likely to be too optimistic, (at least) half the studies were funded by pharmaceutical companies and while I don't want to say you cannot trust them at all, you have to take them with a pinch of salt, especially in regard of how much money they make with flu-vaccination.

Studies funded from public sources were significantly less likely to report conclusions favorable to the vaccines

I do not want to say: "DO NOT GET VACCINATED", especially if you are somehow immunocompromised, be it age (old or very young) or due to some underlying disease (diabetes, etc.), the benefits easily outweighs the risks.