Expanding on my comment of 
>who wants 2nd or 3rd place prize/reward when anyone can have the 1st place prize

The degrees of glory are described in [1 Corinthians 15:40-41][1]
>40 There are also **celestial bodies**, and *bodies terrestrial*: but the glory of the celestial is one, and the glory of the terrestrial is another.

>41 There is one **glory of the sun**, and another *glory of the moon*, and another glory of the stars: for one star differeth from another star in glory.

Mormons belive the Celestial kingdom is like the sun, the Terrestrial is like the moon, and the Telestial is like the starts; as a comparison of glory. The Mormons believe that anyone can attain the [Celestial Kingdom][2], which is the only kingdom where we (man) can continue to progress and where we can be in Heavenly Father's (God) and Jesus Christ's presence forever.

I want to answer this question by asking a question in return: Why wouldn't you want to receive all the blessings God has in store for you? God has given us everything and all he asks in return is 10% (tithing) in return and to keep His commandments which he will then bless us for keeping. Man has [agency][3], so it is up to you what commandments to follow or not, and you will be [rewarded][4] for what commandments you keep.

See also

[Kingdoms of Glory][5]


  [1]: https://www.lds.org/scriptures/nt/1-cor/15.40-41?lang=eng#39
  [2]: https://www.lds.org/topics/celestial-kingdom?lang=eng
  [3]: https://www.lds.org/topics/agency?lang=eng
  [4]: https://www.lds.org/youth/learn/ss/commandments/blessings?lang=eng
  [5]: https://www.lds.org/topics/kingdoms-of-glory?lang=eng