Why is my pension marital property, when I earned it solely through my work, and I haven’t gotten it yet!

A pension is marital property because it is viewed as part of the compensation you received during the marriage, as were your wages, bonuses, commissions, etc. Your wages went to the benefit of the marriage and were therefore marital property. So all parts of your compensation were, and are, marital property. Presumably, you could have negotiated a higher wage, which have gone to the benefit of the marriage, if you had forgone the pension put-away.