As someone who previously worked in ecommerce marketing, many of these practices certainly would cause more drop-off in the funnel.

I would suggest that the idea is that losing X% of first-time customers isn't such a big deal if you can increase LTV by Y% through marketing efforts otherwise not available to you.

That being said I don't really think the average marketing team has thought it through to this point (or measures the outcomes). But nevertheless it's perhaps why they see positive results.