Quando você usa um tablet, a senha do PIN exibe o teclado numérico em vez do teclado de tamanho normal, o que facilita a digitação da senha. É semelhante ao recurso Simple Password
no iOS.
Cite de Construindo o Windows 8 blog :
In a world with increasingly strict password requirements—with numbers, symbols, and capitalization—it can take upwards of 30 seconds to enter a long, complex password on a touch keyboard.
Other touch experiences in the marketplace have tried to tackle this problem, with the canonical example being a numeric PIN. A PIN is a great solution: Almost everyone has seen or used one before, and a keypad is simple to use with touch. We knew though, that there was room to improve.
Além disso, um PIN de 4 dígitos (que tem 10 possibilidades independentes cada) possui 10.000 combinações exclusivas.