I know there is but its not that big.
In Bo1 luck is a huge factor, in Bo3 luck has far less on an impact and consistency is also far more of a factor in a Bo3, you cant just have a strong little streak in the game and win off of that in a Bo3.
"also in bo3 teams can throw/not try in their opponent pick if it isnt going well and try their hardest final", they can do this but thats only bad for them, and if they lost their pick then they cant, Bo3 isnt perfect, Bo5 is better, but Bo3 is the minimum.
Bo3 and 5 gives you time to more accurately separate luck from skill, it also test map pool something that separates the best teams from the teams jut below them.
Its clear to me you know very little about pro CS, its very possible in a Bo1 to end up on a map that you dont really like and thats not fair.