Why are soft bans still a thing?

Can someone explain to me why are soft bans still a thing? I wanted to do some gold Reroll and cant do them because I bought some players and the game says hmmm thats eneough. I bought around 150 players. I want to spend my hard earn coins please let me do it. I cant be on the game everyday for 10 hours. If i want to do something please let me do it. I made around 100 rerolls evry week no problem. Today I am soft banned for like 30 minutes and cant so nothing. This really bothers me