Do you experience heel slippage in your slip on shoe styles (loafers, flats)? Do you have a high arched foot or two different sized feet? If so, you may want to check the vamp length.
The picture above shows two different vamp/tongue lengths on slip on styles of shoes with elastic insets. The brown shoe has a shorter vamp length and the black shoe has a longer vamp length.
For this person the brown pair barely stayed on, because of her very high arch coupled with the short vamp length. The black shoe on the other hand, made much more surface area contact with the foot (think form fitting), creating a much more secure environment.
This is also important if you have one foot shorter than the other, because the short vamp won’t contact the foot enough to stay on, hence slippage or even falling off…especially if you’re running to catch a cab and you forget to hold the shoe on by gripping with your toes!