Because come July 1, that shit's gonna cost you.
Anyhow, starting July 1, all Washington state parks will charge $10 per day per vehicle, or require a $30 "Discover Pass," which is good for a year and can be purchased here.
The new fee system is a result of Senate Bill 5622, which requires the park to charge the fee, and was touted as being the only way to keep the parks open at all.
There are a few exemptions, like if you're camping (the fee is included in the camping fee), have a Sno-Park seasonal permit, or have an Off-Road Vehicle, Disabled Veteran, or other State Parks pass.
Additionally, one can volunteer for 24 hours or more on an agency-approved project and get a free pass.
Getting caught without a pass will cost you $99.
And yes, you will still be paying taxes to support the parks as well.