Texting short of knowing one's phone number has no "identity", is primary used as a communication tool whereas WhatsApp can be considered a "broadcast" tool and relies heavily on it's identity. Short of logs of the conversation for a very brief time, carriers aren't mining text data for advertising purposes or really at all.

Overall this is splitting hairs. If I send you a text message you're not going to suddenly be bombarded with relative ads, posts, etc to the subject we just discussed. I personally haven't used WhatsApp but after a brief google search it appears like an iMessage clone with the data going through Facebook's fingers with data being collected for whatever purpose they see fit.