Why was King Tut not buried in a pyramid?

The age of Egyptian pyramid-building ended over 1000 years before the time of King Tut. Pyramids were too easy to rob and too expensive to build. In King Tut's day the kings were buried in secret tombs in the Valley of the Kings. Still, that didn't stop a lot of tombs from being robbed. Also, even if the Egyptians were still building pyramids in Tut's day, he was such a minor figure that he wouldn't have been given one. The only reason he's famous today is because his tomb was discovered largely intact and contained a lot of treasure.

There was only a brief period in history in which pyramids were constructed. As for tut, he was buried at the age of 18 after they had already stop building pyramids..as mention in the previous answer tut was buried in a secret tomb located in a spot know as the Valley of Kings...

P.S. The reason tut is so widely known is not because he was a great ruler but simply because when his tomb was found it had seemed to be nearly untouched by tomb raiders and therefore it was a great find in the science and history world...

i think that he was burried in a pyramid thats how carter found him

They were still working on a pyramid for him but he died at anearly age of 19
and the only place they could bury him was in the valley of the kings.

The sheer cost and effort of constructing a pyramid. It would have taken the resources of the entire country.
And Pharoah Tutankhamun was only a very young man, possibly sharing the throne with other siblings. And the builders knew that the pyramids were not secure. The main reason whu tut's tomb was not found was that the entrance was covered by rubble from other tomb robberies, back in that time. Have a look at archaeology websites.