Calling alI Inventors!

Coming home with hands full of shopping bags, the other day, having to fish in my bag to find a door key, insert it in the lock and turn it, all whilst juggling bags, I wondered…. Why doesn`t someone invent door keys for houses the same as car keys, that you just have to press, or the even more posher modern ones where you only have to be in the vicinity of the car door and it will unlock for you?
I suppose perhaps there is some reason why it`s not been done, but I can`t think what! It would make life so much easier. And in these days of modern technology surely someone could come up with some secure method of doing so.