The real reason is that they have limited supply, and people want them. (people may not want bitcoin in the future btw) People always want gold and they want to gather as much as possible in their lifetime. It is the only solid asset which holds its true value through the centuries.
This is so true. The thing is, if it is limited the price will rise. Just like in economy, if the demand will rise but the supply is out of stock then probably the demand that is there will have a high price. Gold is a solid asset yes its true, but the volatility we are talking and possibility of a great price hike does not belong to Gold.