I don't have steam, because I've had no use for it. Being able to communicate in BL is far from a reason to get steam for me. Even if I had steam, I wouldn't use it to replace RTB in BL for I wouldn't want to mix my BL friends and steam friends together, they're two entirely different things for me. BL friends are for BL and BL alone.
Sure you can use steam for it, but it is no option for a replacement.
I just hope Badspot makes an official chat & friends system for Blockland.