Hard drives with multiple heads?

Question

Hard disks

Probably a stupid Friday question, but I couldn't find an answer to it :)
Why are hard disks still equipped with only one row of heads? Why not put at least one more block on the other side of the disk? This applies primarily to 15K, of course, there at least you can find a place.
In general, I think about it and want to understand why there are still no such models? Waiting for the market or technically impractical?

Answer 1

this will increase the cost of the disk + it is necessary to develop according to the new data reading logic and the cost of the board layout and the result may not be justified low imho

Answer 2

1. Savings will come only on pancakes.
2. It is not economically profitable to develop such a solution.
3. Simultaneous access to the same sector from different head blocks kills the idea in the bud.