Speaking to the folks at AndroidPIT at MWC 2018, Samsung’s Director of Product Portfolio & Commercial Strategy Mark Notton revealed the reason why, and the reason is because Samsung wanted to perfect the tech first before it is released. According to Notton, he claims that Samsung wants to ensure that when they do release it that it works 100% of the time as it can lead to frustrations features don’t work properly as advertised.
Based on what Notton said, it sounds like Samsung is still working on the tech as he suggests that it is possible that the feature could arrive in future Samsung handsets. Unsurprisingly he does not mention when, but a rumor from last month suggested that the Galaxy Note 9 might not even feature the technology, meaning that maybe Samsung could be saving it for a release in 2019.
In the interview Notton also said that Samsung listened to their users and moved the fingerprint sensor to a more accessible location, and also upgraded it where it will work faster than its predecessor.