your ISP just sees what sites you connect to, but not what you do
Anything that isn't encrypted can be collected and sold by your ISP. Steam, for example, uses no encryption whatsoever. Your login information, chat history, and all your account activity that isn't handled through one of steam's web api's (because their website is https). So in reality,
Signed into steam (Username: BobMcJoe Password: imgay), talked to friend about gay stuff
They already have this information.
You're naive if you think that the majority of your communications are encrypted.