For the Dyson at least, you can remove the sole plate from the base (just use a nickle or something, turn the 2 or 3 sloted “keys”, and pop the plate off). Around the edge, you will see a black foam rubber strip. That strip is an unnecessary item, and you can just pull it out. Replace the sole plate. Now, the suction (and moving air) can get out a little around the sides, makes it stick to the floor a little less.[br]
As to why the suction has increased from what it once was, I don’t know. Perhaps the motors gain RPMs with age as they wear down, but that’s just a small guess.