Okay, the misinformation is getting a little out of hand here. DigitalOcean certainly aren't charging you to erase your data, all you have to do is check the "Scrub Data" checkbox. Yes, you have to pay for the time your VPS is on while erasing, but that's perfectly reasonable.
Why would that be perfectly reasonable? They have an obligation to not make my data available to other people, I don't give a rats ass about the technical details of doing that.
I could argue that it benefits the customer as well.
If it costs DO more (because of disk wearout) then in theory they would have to raise prices in order pay for their higher costs. And those higher costs could then disrupt the balance in pricing that makes them attractive.
My point is that forgetting the numbers you can't say it only benefits them. Being able to offer lower prices (because your expenses are lower) also benefits the customer as well.