The issue starts at the fact that it’s difficult to find a computer sold by a common major distributor with Linux already installed, nor does Linux have any marketing aside from word of mouth to compete with the aggressive Microsoft/Apple duopoly.
The threshold to entry begins at simply having the technical prowess to install an alternative operating system on one’s computer, which I don’t believe a good majority of people are even capable of. Before that, people also need an incentive to transition in the first place. They’ve probably been using their current OS for a good portion of their life and are more than comfortable with it without putting themselves through another learning curve.
The average person isn’t considering an alternative to what they’re already using, and if they are, it usually isn’t Linux. The biggest problem isn’t appeal or ease of use; it’s exposure and immediate accessibility.
That said, performance and simplicity would be an excellent selling point for Linux. It would be absolutely worth banking on the open-source nature of it to appeal to a growing demographic of people interested in privacy-oriented tech as well.