BTC is the first crypto coin and with regards to How long it has been in existence, it is therefore trusted by multitude unlike other coins that sometimes turn out to be a scam.
It isn't only about the trust but its about the adoption that its getting worldwide.
People don't just want to use and invest to a coin that's not so familiar with them and bitcoin has real usage. Unlike other coins that are also taking the title of bitcoin and wants to replace its throne, they don't have use case and that's why it can't take over bitcoin's worth. Maybe someday in the future, a coin will reach $5,000 - $10,000 but imagine on how high bitcoin would be by that time.