watch only wallets

a watch only wallet is for the purpose of watching an account you have in cold storage more or less right? i noticed i can still send and recieve thru it tho so how does that make any sense? if its watch only, why am i able to withdraw from it and send to it? thats not watch only lol

edit: i used pub key not private key. it says watch only wallet. i have only deposited into the watch only wallet and havent tried withdrawing. this is in blue wallet but idk if this is exclusive to them. thanks for any responses.