I think you guys are missing the point. Game trainers are cheat codes that won't come with any paid game. Steam or otherwise.
Anyway @ the OP, I've been to cheat happens.com looking for trainers, and NO, I'm not paying into a subscription, especially when you can find other trainers & cheat codes elsewhere. I know I was looking for one for Prototype 1, and though it took a bit to find a good one, I did.
One thing you need to be very careful with though... making sure you find legit sites to get your trainers from because they're very easy to slip malware in. This is where cheat happens subscriptions come in, they claim their trainers are 100 percent free of malware.... thus the based fee subscription. And (I'm not sure) I think those uploading their trainers pay as well, so it's all very controlled.
Is it worth it? How important are trainers to you? Only you can answer that.
And if their files are as clean as they say they are, and you use a lot of trainers, well...