DFirst1

Answer: Probably for multiple reasons. For the movie, having Aragorn struggle against his own desires and an inherited destiny makes for a more conflicted, intriguing, and three-dimensional character rather than the stereotypical power-obsessed trope. Being king is an immense responsibility and a heavy burden. Personal wants and freedom are sacrificed to serve others. Not every ruler craves power and oftentimes were born into an unwanted, pre-destined path. Aragorn was raised in Rivendell, unaware he was the heir, nor was he groomed to become king.

raywest ★

Answer: Because he wanted Gandalf to join him. There are only five wizards in Middle Earth, and for Saruman, having a second one on his side would basically mean the Elves, Dwarves, and Men didn't stand a chance.

Friso94

Answer: There is a little bit more to it. There is a scene in the Extended Edition of the second movie where Faramir flashes back to when he and Boromir successfully reclaimed Osgiliath from the forces of Mordor, and in the celebration afterwards, they are approached by Denethor, who informs Boromir of the Council of Elrond and that he suspects it's about the Ring. Denethor wants Boromir to get the ring and bring it to Gondor, to use it. That is why he is so hell-bent on leading the Fellowship past Minas Tirith: he wants to take the ring there.

Friso94

Chosen answer: No. He joined the Fellowship to help destroy the ring, but he did not have enough willpower to resist its call. He thought he could then use that power to defeat the enemies of Gondor.

Answer: Initially the Fellowship was meant to accompany Frodo to the south, with Gimli and Legolas branching off to go home and then Aragorn with Boromir headed for Minas Tirith. As the journey continued the band bonded and after Gandalf went down with the Balrog priorities shifted; Aragorn and Legolas now wanted to go to Minas Tirith with Boromir with Gimli wanting to go with the Hobbits. Boromir was haunted by his dedication to his father and his city throughout, something Galadriel noted when they met. We get a better view of this in the Two Towers; Faramir warns Frodo that if they went to Minas Tirith with Boromir they would not recognize that Boromir, who was tempted with the Ring in a way his brother was able to resist. Boromir did not want to take the ring initially but his lack of options made him want it at last, leading to Frodo abandoning everyone.

Answer: Because he was holding the most powerful object in the world, the one ring. Even when he only just got it, its powers are not something to take lightly. If Isildur decides not to destroy it, there is nothing Elrond could do to stop him.

lionhead

Answer: Yes. It was Isildur's by right, having been the one to shear it from Sauron's hand and thus defeat him in combat.

Phixius ★

Chosen answer: Virtually everyone was vulnerable to the Ring's power to some extent, even Frodo Baggins. Frodo's purity of heart and incorruptibility made him the least affected by the Ring and made him the only logical choice to actually carry it for the duration of the mission; but EVERYBODY was vulnerable to its seductive power, some just more so than others.

Charles Austin Miller

Chosen answer: Sauron lost the ring when his mortal form was destroyed and Isildur cut it from his hand.

Sierra1 ★

Chosen answer: He might have done, if he'd gone alone (or only with his fellow hobbits), but the rest of the Fellowship, particularly Aragorn and Gandalf, knew Middle Earth so well that they didn't need one.

Chosen answer: Most of the paths they took (e.g. over the mountains or through the Mines of Moria) would have been impossible to cross with horses, and besides, horses would have necessitated carrying a lot more gear and food, which they couldn't be bothered with.