The problem is that every fix that you could think for Spectre reduces the performance of the CPU.
So not enabling this by default it's a good choice, Spectre is very difficult to exploit: so if you do critical things you enable the fix, if you use the computer for gaming, video rendering, and things where you don't care too much about security but you care about performance, you don't enable it.
So not enabling this by default it's a good choice, Spectre is very difficult to exploit: so if you do critical things you enable the fix, if you use the computer for gaming, video rendering, and things where you don't care too much about security but you care about performance, you don't enable it.