[danhor]

AFAIK wind turbines, as opposed to conventional turbines in power plants, don't directly connect to the 60Hz Grid but go through DC and an inverter. This is done so they can efficiently work at different speeds at not just a few mechanically selectable ones

[shadowgovt]

They have to, because the variable wind means that they need to be spinnable at a continuous range of speeds.

Components connected to the AC grid need to synchronize with the grid's frequency. Since we can't force the wind to blow at a particular rate, we'd either need a lot of fancy mechanics on the turbines themselves to drop their speed (which would waste energy) or we decouple their spin rate from the grid frequency with the AC -> DC -> AC converter (which also wastes energy, but probably less and with much less cost than complicated spin-rate-stabilizing machinery).

[sudosysgen]

You could also have a continuously variable gearbox, which is still hugely problematic, but would waste less energy.