That's not taking the whole dick lol even in porn women can't take it full, I'm assuming this because you need positions to take control over it, makes sense if guys don't know how to use it if you are doing this all the time. However that's another reason why size matters. A 7inch penis can do the same and plenty more than a 5 inch penis with the same girth, only if the guy is skilled enough (as a guy, bigger dicks are more difficult to control, because you can't go deep always). Guys don't have to use the whole length, but clearly is beneficial to have the extra length when needed, hence size matters.

Some women need to figure it out how to enjoy the stretching feeling when it's a little bit more than normal and how to be able to enjoy deep penetration without smashing the cervix if you don't like it. Wait for that golden guy.