Because the rebate is a fixed amount while the tax depends on your emissions. Even if you’re paying little/no net tax, you still have an incentive to lower your emissions to keep even more of the rebate. So it amounts to a reward for good behaviour, rather than a punishment. https://twitter.com/andrewbellbnn/status/1318561271290204160

While policies like e.g. giving tax credits to people who make their homes energy efficient are an easier sell to voters, carbon tax/rebate really has a similar net effect; it’s a reward for people who are ready to make changes, not a punishment for your current lifestyle.

The advantage of the carbon tax though is it rewards all emissions reductions equally, regardless of how they are achieved. This is far more flexible and efficient than having the gov’t pick and choose which behaviours to incentivize.