My partner works in the public sector and can not buy holidays, I know friends in the private sector who can.
Must depend on which part of the public sector you work in then. In my experience, that was the leave model. You could get 35 days leave in one year - so, seven weeks. And it was common for people to take it.
Other people I worked with also took advantage of the EU entitlement (gone now…) to take 18 weeks of unpaid leave per child, which could be claimed up until the child is 18. One colleague used that plus annual to take all summer holidays each year.