This will just be a simple pros and cons list of using Loadstring in Roblox Lua:
-Your game can run lua code directly without you having to implement your own interpreter.
-You can run commands from a 3rd party server without you being in the game
– Your game can enable more creative freedom to players by being allowed to mess with the gameplay of your game
-It can cause a devastating experience to players causing them to never re-play your game.
-If an exploiter gains access, they could teleport all players in your game to a scamming game where they are forced to buy stuff
-Exploiters could run profanity in your game causing it to be shutdown by Roblox for review.
-All of the above reasons and then some.