"Forward error correction" is really just the application of ECC while transmitting data over a lossy link in order to tolerate errors without two-way communication.
The ECC used in memory is likely relatively space inefficient at the benefit of being computationally simple so it can be done quickly in hardware. More redundancy could be added to tolerate more bit flips, but it would either add a lot of memory overhead, or a lot of computational complexity. In particular, something really good like reed solomon would likely be very difficult to encode on every single memory write, at least not without taking a several order of magnitude performance hit. It would likely be easier just to have 2x ECC memory, or 3x non-ECC memory and do majority voting.
The ECC used in memory is likely relatively space inefficient at the benefit of being computationally simple so it can be done quickly in hardware. More redundancy could be added to tolerate more bit flips, but it would either add a lot of memory overhead, or a lot of computational complexity. In particular, something really good like reed solomon would likely be very difficult to encode on every single memory write, at least not without taking a several order of magnitude performance hit. It would likely be easier just to have 2x ECC memory, or 3x non-ECC memory and do majority voting.