It is very inconvenience to have No RBF transaction. Because if mempools suddenly loaded and congested, the user will have only one choice, using Child Pay For Parents but it requires more expensive fee than using Replace by Fee to increase the fee. It also requires the user has control of the receiving transaction that sometimes the user will not have that control.

Not all times we will need to use RBF but always have RBF opt-in for all transaction is good as reserve for emergency when we need bumping fee for a pending transaction. We can completely control it.

No RBF only can be accepted in mempools that support Full RBF but not all do this.

https://mempool.space/rbf#