Bitcoin would literally have no value if no one uses it, there will be no concept of demand/supply of it basically. So we can say that popularity of it is a very critical as it would increase its value, they go hand-in-hand as increasing value also attracts investors.
Exactly. Bitcoin's value is only determined by its usage and adoption in the real world. It's just a mere combination of ones-and-zeros with absolutely no value at all, since it's not backed by anything real. However, given that Bitcoin's blockchain is the most secure to date, its transactions are immutable, and its supply is finite, it's no wonder why it has value. The creator of Bitcoin designed it as such, to be a deflationary currency, unlike many real-world currencies we know and love today. Because of this, the future value of Bitcoin is in people's hands. No central authority means there's no single entity that's responsible of giving value to the cryptocurrency. As such, Bitcoin is a cryptocurrency by the people, for the people in this world full of corruption and fraud.
Only time will tell what Bitcoin's value will be in a few years from now. Just my opinion