The concept you're looking for is "savings". Contractors and freelancers charge a premium to compensate for the lack of income stability. If that premium is saved up, you get stability.
Relying on savings to compensate for irregular income requires you to have a runway to begin with.
Given the increasing mountain of debt new graduates start with, this is going to be generally untenable for most new employees; and even some older employees will have enough financial obligations that building up the requisite amount of savings to account for income irregularities would be very difficult.
Getting to the point where you can deal with uneven income flow can take quite a bit of time, time you need to spend working for someone.
