Why havnt we seen some parents in Naruto? It's weird, really weird if you ask me...
Huh?

We have seen plenty!
If you think about it, It`s only Sakura, Lee and Ten Ten of the original Konoha 12 that doesn`t have any know clan or similar. Also we could count Sai in.
Regarding the others:
Neji and Hinata: Hyuuga clan - Byakugan.
Choji: Akimichi - Multi/double size techniques.
Ino: Yamanaka - Mind transfer techniques.
Kiba: Inuzuka - Dog senses and dog jutsus?

Shino: Aburame - Bugs.
Shikamaru: Nara - Shadow techniques.
Sasuke: Uchiha - Sharingan.
Naruto: Uzumaki/Namikaze - Large chakra, Sealing techniques?
Rock Lee: Lee? Rock?, Rokku Rii??? - ?
Sakura: Haruno - ?
Tenten: Yukari: Weapons?

Sai: ? - ?
Regarding the parents. Everyone knows the father of Choji, Ino and Shikamaru, They`re famous. Also we`ve seen Shikamaru`s mom. Not sure about Ino and Choji.
Hinata and Neji: We`ve seen their whole family(almost at least

)
We have seen Shino`s father, mother and brother I think. At least father.
We`ve seen Kiba`s mom and Sis. Father?
And you all know about Naruto and Sasuke
As for Rock Lee, - None. Tenten, - None. Sai, - None. Sakura, - Heared her mom,- maybe seen her in a flashback from when Sakura was a child?
That`s as far as I can think of needs to be mentioned in this thread
