zelda-breath-of-the-wild
If I can remember right, no reason is given in Zelda: Breath of the wild as to why the robots that were used to defeat Ganon 10000 years ago were then buried and forgotten by pretty much everybody.
Did the sheikah from 10000 years ago see the "Ganon hacking everything" plan coming, or was their use done so they just let them get buried over time?
Once you purchase the house in Hateno Village for 3,000 rupies and 30 bundles of wood, you will get one weapon rack in that house which allows to store one weapon in it. Though I haven't tested it in the long run I'm sure that the weapon you put in will not disappear when you come back.
You can then buy more furniture from the same person you bought the house from, allowing you to get more weapon racks among other things.
According to the Official Guide, the completion rate is shown on the lower-left corner on the Sheikah Slate's map, and adds up by .08% for every "relevant objective", which could be tasks such as;
Hope this helped!
Best Answer
While nothing is concrete, it appears that the Sheikah either A: Became outcasts and were feared by the Hylian people or B: Adhered to the royal family's warning, and forgot their creations and left them to be buried.
(The quote came from here)