I think the much better question is why would somebody use OP_RETURN for stamps, BRC-20 and Counterparty. It does make a difference for some of these protocols if the data is in an output, or the scriptsig, or witness part of a transaction.

Hi Sjors, appreciate your explanation, but which 'protocols' do you address here (below)? I mean, Lightning needed a softfork, we tacked on some privacy improvements later, but I'm unaware of other high prio things still being addressed... And if applications need data before spending, why not ou...

This also illustrates that if we had made this change earlier, they would not have designed the system to create unspendable public keys in the first place. They have no financial incentive to deviate from the original design. And once such a system goes live, assuming it has any uptake, their engi...

It's easier for a light client to obtain data in an OP_RETURN too - you only need the block merkle root, for witness data you'd need to get the coinbase tx and the witness commitment as well.

I think your last paragraph in the answer needs some edited and expansion. It confused me a bit