Shielded by default or opt in depends on the wallet you use. As you can imagine, a lot of people like shielded by default. There are reasons to have transparent transactions btw. You may want public proof.
Again, it is not the same as bitcoin. Using a mixer does not come with ZKPs. The transactions are also still public. You can see how much was put in and how much was taken out. Worse, you now potentially have traceable tainted coins and a target on your back.
The point of Zcash is the Z. Zero knowledge proofs. Monero uses differential privacy. Zcash has much stronger privacy guarantees.
Again, it is not the same as bitcoin. Using a mixer does not come with ZKPs. The transactions are also still public. You can see how much was put in and how much was taken out. Worse, you now potentially have traceable tainted coins and a target on your back.
The point of Zcash is the Z. Zero knowledge proofs. Monero uses differential privacy. Zcash has much stronger privacy guarantees.