Deleted scenes allow fans to make a movie they love even longer. Sure, most of the time those scenes were deleted for very specific reasons, but seeing them is always like getting a few extra presents on your birthday. They make what was already good, even better. This goes doubly for a film as massive as Avengers: Endgame
Source: io9 – The Writers of Avengers: Endgame on Why All Those Deleted Scenes Didn’t Make It Into the Movie