Adding spouse income reduces tax refund

[varunlibra3]

Me and my spouse generally submit our returns together.
While preparing my tax returns individually, I was getting a refund of around CAD 2000.
But when I added my spouse's income, the refund got reduced to only CAD 1000.
Both of us have around the same income and are full-time employees.
Why is it so? Shouldn't the tax refund increase?

[TurboTaxSusan]

This FAQ explains why your spouse's income lowers your refund amount: https://turbotax.community.intuit.ca/replies/2647826