Hangouts includes a lot of added extras too, including text - based instant messaging, stickers, and support for calling regular phone numbers, for an extra cost. (t3.com)
Though it's arguably a niche issue, it is frustrating for Google Voice users: an issue that causes texts to be sent using one's regular phone number in certain cases. (slashgear.com)
Many users report that, in this case, sending a text results in Hangouts sending the text with the user's regular phone number instead of Google Voice. (slashgear.com)