BTC has value because it is popular which is why people accept and trade in BTC because others also does the same. Also, BTC is decentralised and limited(Hard cap) unlike and endless supply of fiat money being printed by central banks on a regular basis.
TL:DR BTC has value as long as people believe in it.
yes, I agree with you, bitcoin is high due to increased spreading and bitcoin volume. when many people use bitcoin and invest in bitcoin, the value is higher. and also decentralized bitcoin, so its value is no maximal limit.