Well said, Anabel.
Even without veto power, there's always The Ultimatum. In my experience, relationships that exercise ultimatum power doom themselves. It's a bad sign when your arguments involve "Choose what I want or else I walk." Note the difference from "My needs in this relationship cannot be met under these circumstances."
The notion of veto power with no explanation or justification frightens me. That obviously indicates a lack of communication and abundance of insecurity. Our relationship couldn't function the way it does if we didn't understand the way the other one ticks. Anything serious in life requires explanation and justification, it's part of the deal when you're sharing a life together. I'm not talking about every little coffee date or new dress. But spend enough time with someone, you should know what's important to them and when they'd like to be consulted. If you have any trust and respect for them, you'll consider their concerns.
“As I am sure any cat owner will be able to tell you,
someone else putting you in a box is entirely different
from getting into a box yourself.” —bisexualbaker