Re-reading the Lord of the Rings, Chapter 11

The whole point of getting to Weathertop is to get close enough to Rivendell to signal for help.

Sauron can put fire to his evil uses, as he can all things, but these Riders do not love it, and fear those who wield it. Fire is our friend in the wilderness.’

‘Maybe,’ muttered Sam. ‘It is also as good a way of saying ‘‘here we are’’ as I can think of, bar shouting.’

But Aragorn also has another reason, he wants to fight the Ringwraiths.

There live still those of whom Lúthien was the foremother, and it is said that her line shall never fail. [...]

As Strider was speaking they watched his strange eager face, dimly lit in the red glow of the wood-fire. His eyes shone, and his voice was rich and deep.

The reason why Tolkien leads Frodo into this calamity is, because he needs to change the nature of his journey. It was, so far, his journey, he was more or less on his own and its nature was to hide from danger. This way Tolkien could focus on Frodo and properly introduce him, but now he has to end the ridiculous concept that the Elves would care so little about The Ring that they would let their own men be outnumbered by Sauron's right at their door-step in Eriador.

There are those, who can and will fight. The Hobbits, though, don't do too well on their first attempt and Frodo gets an ugly wound.