This may not affect every Android user reading this, but it’s unfortunate news nonetheless. Android Police reports that G Suite administrators have received email notices from Google warning that SMS will no longer be supported in Google’s de facto chat app as of May 22nd. Affected Hangouts users will be seeing the above in-app alert starting March 27th.
Hangouts has supported SMS since Android 4.4; those who made use of it—myself included for a time—enjoyed the benefits of needing one less icon on their home screen and, more importantly, having all of their non-email messages contained within a single app.
I can think of at least one technical reason why the change needs to happen: with RCS coming to text messaging it might be too daunting for Google to add Hangouts support, especially when Hangouts itself is already undergoing a fairly significant makeover.
There may well be another, more pragmatic reason, as a redditor on this r/Android thread explains:
Hangouts Users: “Why would I use Allo when Hangouts has IM and SMS?”
Google: “Good point…. Aaaaand fixed.”