The title of this article in itself is a little bit contentious as in most cases the answer will always depend upon the situation.
That said understanding where and when to use the trap/ hex bar should be a priority of most forward thinking coaches looking for best practice. The trap bar in itself is often favoured as the loading and hand position makes it pretty easy for those new to the weight training arena to adapt and adopt without finding that technique may be compromised.
Straight bar deadlifting form can often be compromised by poor hip and lower limb mobility as well as weak spinal erectors meaning it is harder to get into the right positions to develop the movement in a safe and effective way.
A recent study by Camara et al. (2016) used individuals who could deadlift 1.5 times their bodyweight. This is interesting as most studies don’t used trained populations- in this case it means that there was a level of mastery for the individuals involved in testing.
Maximal amounts lifted didn’t vary but the peak force and peak velocity were different. This highlights that from a force production point of view that the trap bar may be superior.
From a muscle activation point of view the vastus lateralis (part of your quads down the front of your leg) was more active compared to the erector spinae and biceps femoris (part of the hamstrings down the back of your legs). It brings home the point that the hex/trap bar is not as posterior dominant as the deadlift is when looking at things from a muscle activation point of view.
So is there a reason to remove deadlifts from programming? Not necessarily, the use of any exercise depends upon the context of the athlete. This study highlights that force production may be developed more favourably for a while with the use of hex bar. The role of the quads is obviously enhanced here as it is somewhere between a squat and deadlift. As there is less erector spinae activation (back) it means that there is less stress placed upon the musculature of this area which may be a limiting factor in developing the deadlift e.g. poor hip mobility and weak erector spinae make full deadlifting a bit of an issue.
The trap bar in my opinion tends to be easier to coach than a full deadlift and it makes it an easier catch-all lower body drill. It is a good compromise to help develop physicality especially if mobility issues limit the performance of an effective deadlift. In turn deadlifting may be considered a progression from hex/ trap bar lifts as it challenges the posterior chain and therefore may be a good advancement.