If I'm an employee: that they're mine. My employer has no claim on all of my time.

If I'm a consultant: not much, which is why I often work them instead of weekdays. Not both, but instead of.

This is such an aggressive attitude.

Yes, in general, my weekends are mine. I would not work for a company which consistently asked me to work every weekend.

But I'm happy to share one or two weekends a year with my employer.

Moreover, I also consider my evenings "mine." That doesn't mean I'm going to throw a hissy fit when the company has its holiday party.

There's a big difference between working a weekend and partying for an evening. The latter is typically optional (and if its not, that's a problem).

There is no "sharing" with an employer. The employer exists to get as much out of the employee as possible for as low a rate as possible. And drawing bright, do-not-cross lines is the only way to get on with them.