Seabed mining experiments have shown that in thirty years areas ploughed have not recovered at all, thus it is a non-renewable resource, another harm to nature and the ecosystem of our planet. We can either seek rare minerals to make electric cars or change our way of living so that the vast majority of people don't need any sort of car. We need to live within our ecological means instead of "breaking Earths banks" even more.
The seabed, even that in deep waters, has life. All of creation came from this cradle of all Earthlings. And so we make our vow to protect the oceans all all who live in her, to see that Earth thrives long into the future yet unspun.
The seabed is either rich in flora and fauna, or a watery grave of sorts, and so much of this depends on how we chose to live, what resources and gadgets we "need." Until we separate our needs from our wants, the sea bed and marine life are destined to get neither.
The seabed is either the comfortable bed of mother nature or her grave, are we building it up or digging a hole?