The point of canceling in general is either to get the opponent to flinch(like do something risky/make an unspecified, irrelevant reaction) or to desensitize them to the start up(so they react off-time/slower/freeze when they see the real thing or do something else). The more apparent(and threatening) the motion, the more likely to achieve the desired effect.
In 44Bs case specifically, 44B is a long range move that deals good damage and is very safe on block, does a lot of block damage, pushes back while forcing crouch. One possible use of this is as a spacing tool. The major problem is it's linear and slow enough to where an opponent can sidestep in response to seeing you "start doing something". At the ranges the move is most useful, asta's ability to beat step is limited (A+B can be guarded out of step as an example). What canceling 44B(and varying charge timings) does for you in this situation is reduce the likelihood that you will get your 44B stepped and possibly trick them into sidestepping so you can reposition/hit their guard with a + on block move or what have you.
A more general use for 44B cancel is that the motion, both huge and flaming, is more likely to create freezes before a potential mix-up than your standard Ag, Bg, Kg, especially since asta's don't look very impressive.
An unrelated use of 44Bg is that since it recovers crouching, it can be used as a short-cut to FC/WR moves from standing. It doesn't really do a better job of this than just pressing 2G, but it might be easier for some people(and has somewhat less strict timing on the FC/WR move input)
I don't know how helpful that is to you and there are probably more uses than the ones I mentioned.
[edit] also you can use 44B cancel to fake any other chargable UB to create inappropriate reactions i.e. make opponents ground rolling counter-clockwise stand thinking it's a 3_33B into a grab or w/e(some players will stand regardless of which direction they were rolling)