[ves]

well, you may not have their address, but you have their inbox.

“References and supplemental video content available on my website at ...”

[seemslegit]

Great, so now you have a website to maintain and pay for and your customers with their associated revenue are still owned by substack.

Getting paying subscribers to change their subscription method is huge friction and risk of churn, the more revenue you already have established on substack the bigger the risk cost of trying to move away, aka the boiled frog business model.