A Grade 3 scramble is actually supposed to be easier than a Moderate rock climb overall, though in practice they often have short passages of maybe 3 or 4 moves of climbing up to around Severe. Unfortunately this isn't always obvious from the guide book or from inspection, so you have to be prepared for more difficulties than the overall grade would suggest.
A classic example is one of my faves, Cneifon Arete, which starts, according to the guidebook, with about 20ft of 'steep climbing on good holds'; it's actually a pitch of V.Diff on some of the most polished holds I've ever seen.
I don't think anyone would advise scrambling without protection where the consequences of a fall could be severe, regardless of grade. It may appear from a distance that scramblers aren't placing any protection, but in practice they may be placing running belays, which is often all that's necessary to hold a fall on typical scrambling ground. Anyone who doesn't is either confident or stupid, and in either case probably not a good example for a novice to follow.
