Only because treehugging EU morons try to stop them.
Just think about it for a minute, they're actually trying to cut the amount of power used by something which you have running for about 0.001% of the day. It's as stupid as hosepipe bans, when we all know that 95% of water is consumed by industry, not domestic supplies.
I prefer my hoover to actually do it's job, not take twice as long using half the power, which er.... comes to the same amount of energy! Doh!