I am not sure what is the rank of the Sixers in terms of 3 point shooting as a team, but I believe they are not in the top 10 as their offense is more focus on the inside, if they only have Reddick, they could have been a big threat in the outside but Horford would not land to the sixers, it's really hard to choose but I believe they prefer to have this kind of play right now, besides they are doing pretty well at home.
The numbers of threes they shoot ain't that high, their plays are more on inside and perimeter shots. Mostly, Embiid plays.
It works so they stick with it.
Others will leave but the original big 3 will stay, when Curry, Thompson, and Green plays together, they can beat any team in the NBA, warriors just needs to keep these 3, give them the best amount of salary and Warriors will once again a championship contender team as long as they are healthy.
Once 1 of the splash brothers is out the offense is getting worse.
Roleplayers is also needed. I mean, look at Lakers, they have stacks of roleplayers just sitting on the bench.