The minimum maneuver speed (amber band) is dynamic, effected amongst other things by speedbrake and anti Ice, giving reduced maneuver margins. The Flap maneuver speeds are set high enough that this shouldn't be an issue. It also means that a few knots of speed loss here and there won't hurt - if you look at the 'maneuver margins to stick shaker' zig zag chart you'll see that there are sizable margins.
Flap maneuver speeds give nice easy 20kt increments that just makes it simpler to fly. Having said that, if you've got a minimum maneuver speed displayed and you understand what it means then you get a little bit of flexibility when speed controlled on final etc.