Because it’s less resource intensive for node runners.
Discussion
Citrea will choose to make their system more expensive for its users just to help out the node runners?
And even if they did, isn’t citrea open source? I assume it wouldn’t be difficult to fork to a version that uses witness data to reduce costs. Will the market choose to pay the higher fees as a charity to node runners?
You can fork it, but you need people to work on it and build for it.
It seems likely some competitor will offer the version with lower fees. Then the market will decide if the cost is worth it to help out the node runners.
You say it’s reasonable to remove the limit. Does knots allow you to remove the limit on your node? Does core allow you to enforce the limit? What is the justification for not allowing a node runner to choose the policy for her node?