Most pensions at least pretend to be equivalent to a retirement savings account. Defined contribution pensions are effectively a savings account, and defined benefit pensions pretend to be similar (but are usually not).

Defined benefit pensions are usually used for government roles and some large unions, where the unions can get large increases in total employee benefits without having the true cost show up on the organization's books. The union and employer generally agree to use unrealistic numbers for returns on investment (>=8%/yr).