Read receipts are one of those bizarre things that some people love, but others hate. While you should probably just turn them off if you don’t like them, iPhone 6s users can keep them on while still seeing messages with a little 3D touch trick.
The iPhone 6s /”peek and pop” feature allows you to hard press on the screen to “peek” at things like links, data detectors and messages. In the case of messages, it means you can hard press on the message to preview the conversation without actually pulling up the whole conversation. Doing so does not mark the message as “read”, so you can still get the idea of a message’s contents without letting the sender know you saw it.