that sounds good but... isn't grabbing supposed to be the original shield breaker? plus it's quicker! they're going to see you charge up your smash attack or see you about to do one... then dodge behind you and throw you...
Except for characters with awful grabs (Samus, Link, Y.Link), or slower characters that don't land grabs as often.
All you have to do against Samus is turtle in your shield for about half and hour, hit her like once, and wait like 3 seconds for your shield to regenerate, and the only thing they can do is hope for a shield poke or attempt a shield grab, which gets stopped if you jump.
And yeah, it seems to be a trend that noobs rarely shield, but spam roll like no other.