That someone better
If people don't switch it's because the game works for them.
Yes, This is called: "Good Enough".
D&D has the largest network effect of players and GM's. It is by far the easiest RPG to find a game to play in, or to find players for.
People just want to game, and as long as the system is good enough that it does not actively hinder the path of least resistance; that's what they'll do.
Largest Network Effect + Good Enough = No can Defend.