why ,because they take a lot of current to drive thenPower (watts) is equal to voltage times current. If the amp can make the power then it also has the current. You can't have current without voltage- that's the laws of physics. Obviously the above statement is false.
tube donot have the current on demand that good solid state brings , when you have a speaker going
If you want to use tubes and get the bass right on Maggies, first, use a tube amp that has good low frequency bandwidth. Second, use monoblocks so you can keep your cables short, and by that I mean maybe about 1/2 foot. Back the amp up to the speaker and use that short connection- which should also be fairly heavy. We have a lot of customers with Maggies because Magnaplanar is here in town and people want to put our amps on their speakers- both are known for transparency. So I've done this a lot- it works. The usual YMMV due to standing waves in rooms but that has little to do with tubes.