Those 4 bytes have barely consumed over a megabyte in the 300k+ blocks we've mined.
It's copied and stored a million times, why not use the space more economically.
I see 2 options,
- either it's removed by convention, (or maybe used for special transaction, maybe we could randomly gift the privilege of using the space to the node that broadcasted the transaction?)
- compression, just remove it and spoof whatever is required (compression seems very underutilized)