I don't see any reason to buy the Premium dice bot or whatever script people are selling. In the long run, House always wins. Making money with whatever bot is not guaranteed.
Maybe those premium dice bots have something new to offer than the free ones but you are right. Winning is still not guaranteed. Bots can only help us to roll faster or to automate the process like when we look for a certain number or multiplier. This is useful if you are joining some dicing contest/promotion like what we often see in primedice.
Not sure what new they could offer. Most things come from the casino side, and Those bots only help you execute your strategy. Nowadays, some casinos like the wolf and duckdice offer lightning-speed dice that can be used to participate in wager contests. But, for those casinos that don't support lightning speed betting or faster speed, The bot helps to speed up the bet. I also saw that Dicebot gives errors because casinos limited the betting speed to slow down the players.