The RNLI have pushed the removal of tie-in-a-bow likefjackets for years, as have the RYA. The issue for airlines is the need to change them over almost all at once. Very expensive.
The only good thing about tie-up versions is that you can get them very tight which helps to insulate the vital organs due to the presence of an inflated "thermal barrier", whilst also keeping the body in the right position.