Do LDS believe everyone is called to marriage?
(I'm glad you asked. I'm not Lds, but since Mormon FREEPERS have tended for a while now to be quite shy about answering questions around here, I'll be glad to cite Lds "prophets" with a brief lead-up explanation to answer your question).
First of all, you need to understand the Mormons believe that "families are forever" -- a common bumpersticker among Lds. Hence, they believe both (some) families and (some) marriages is forever.
But that's not true for everyone. They think it will ONLY be true for faithful married temple Mormons. (It's hard to know exact % of how many Mormons are temple Mormons; we've had FR Lds several years ago confirm that he thought about 20% were "temple" Mormons).
Those Lds who supposedly will get forever families are ones eligible for godhood -- IOW those who get to the "Celestial Kingdom." When Mormons talk about "the Celestial Kingdom," "exaltation," "eternal progression," "eternal increase," "becoming an heir," or even "eternal life," those are all codewords or veiled phrases for an underlying reality of, "Yes, we're grasping after godhood"....and is reserved only for MARRIED, TEMPLE, TITHING MORMONS. All others are excluded.
And the cultural reason behind why so many Mormon singles are so barraged with the marriage Q ("when are you going to get married?") is a veiled, "Hey, don't you know that your future godhood is at stake if you don't get married?"
For further documentation, continue reading these two Lds' past "prophets":
...this doctrine of the eternal union of the husband and wife and of plural marriage, is one of the most important doctrines ever revealed to man in any age of the world. Without it man would come to a full stop; without it we never could be exalted to associate with and become gods neither could we attain to the power of eternal increase... (Lds "prophet" Joseph F. Smith, Journal of Discourses, Vol. 21, pp. 9-10)
So if you want to enter into exaltation and become as God, that is a son of God or a daughter of God, and receive a fulness of the kingdom, then you have got to abide in his law-not merely the law of marriage but all that pertains to the new and everlasting covenant... (Lds "prophet" Joseph Fielding Smith, Doctrines of Salvation, Vol. II, p. 63)
So as you can see, Mormons believe THEY are called to become gods. And apparently you can't become a god without a goddess. Hence, they believe our god, who they think was once a man, is "married."