I do get the TX state park pass every year so I don't have to pay the day use fee plus I get half off the 2nd night on up to 4 visits per year. It does pay for itself for me. I prefer the more spread out feeling of the state parks over private parks. At one private park we stayed at last year, we had one woman - full time resident I believe - that would wander through our site in her housecoat, picking up pecans. And the sites, while big for private parks, were still tight. And we had to bring our own fire pit to be able to have a campfire.
I want room to be able to set my camp kitchen and be able to cook outside. I want a place where I can have the dogs outside and not have to worry about them encroaching on someone else's site. And most of the private parks I've stayed in have been more expensive than the state parks without the day use fee (since I've already paid that with my state park pass).
And for those of you not from TX, TX is in danger of losing some of its state parks - in fact, one went back to the water authority this year and the price immediately jumped $12/night. At least two parks were hit hard by wildfires last year and almost all of them suffered from the drought. They are just getting Sea Rim back up and running after Ike wiped it out 4 years ago and Galveston State Park is much smaller than before Ike.