Why would I want to keep BTC in my investment portfolio? That's most hyped and quite overvalued coin I'd say.
There are other more technologically advanced coins. Is it because of "digital gold" and store of value properties?
The answer is simply because even there are more technologically advanced coin nowadays, still, the potential that offer by bitcoin is unbeatable by any currency. Even its price now is lesser than before, still, no cryptocurrency can hit that kind of value reaching up to $19,000. It increases its value for 700% per annum and that is the best reason why we keep holding our bitcoin. No other currency can give you opportunity to earn as what the bitcoin offers.