Why is email verification still treated as a separate workflow?

I’m building in the email tooling space, and one design choice keeps bothering me:

verification is still usually bolted on around the send workflow instead of being part of it.

From a systems point of view, that seems odd.

Invalid addresses, disposable emails, catch-alls, stale lists, and poor domain hygiene all affect downstream outcomes like: - bounce rate - sender reputation - inbox placement - campaign performance - how much trust you can place in your analytics

But in a lot of products, the workflow is still something like: 1. collect/import contacts 2. build campaign or automation 3. send 4. separately run verification or cleanup somewhere else

That feels architecturally backwards. If data quality affects the send path, why isn’t verification more commonly integrated into the send path?

My guesses are: - latency and throughput concerns for bulk sends - cost structure and margins - false positives / UX risk - org boundaries between marketing tooling and infra tooling - legacy product architecture - users not wanting extra friction before send

For people who’ve built or operated email systems at scale: what is the real reason this is still usually a separate workflow?