Well, that's one half. Like, Teslas and Nissan Leaf have no transmission at all, they are direct drives. That's a hell lot of sensitive gearing gone. Also, the load on brake pads is much lighter because breaking is regenerative and so instead of needing to waste away all the energy of the spinning wheel as heat on the brake pads, you just use it as a generator for a while.
But in general, there are less consumables, so to speak. Like oil filters, what oil filters? An electronic cable has a lot less chance to break than a seal to grew old. No spark plugs. And, again, see brake pads above. Still some parts require maintenance (wiper blades) but much less.
Current Teslas [1] along with the Nissan Leaf and Chevy Bolt all have single gear transmissions with a ratio of about 8 to 1. It is true that these are very simple transmissions that never need to shift, which should reduce complexity.
1. Very early Tesla Roadsters had 2 speed transmissions.
But in general, there are less consumables, so to speak. Like oil filters, what oil filters? An electronic cable has a lot less chance to break than a seal to grew old. No spark plugs. And, again, see brake pads above. Still some parts require maintenance (wiper blades) but much less.