Password required for child accounts to ask to install an app?

I purchased iPod touches for my two kids (5 and 7). I setup the ask to buy apps. Why do the kids need to enter a password each time to just to ask to install the app? Personally, I do not want them knowing the password to the account as they would probably tell someone that should not know it. I got the touches for them as I want to transition them to iPads later from their android tablets they use now. There has to be a better way do them to simply ask to install the app. I have both Apple and Android tablets and Android just simply sends me a message to approve and no password is required from them. Is there a plan to fix this in the future?