1. Burner emails can be used for long-term use.
Temporary emails are great for one-time use and typically expire within 10 minutes or so. However, what if you want to be able to continue to receive email privately from a sender? Burner emails are great for signing up to new SaaS tools, eBooks and newsletters because they will continue to be forwarded to your real inbox up until the point you decide to mute those services.
2. Burner emails are easier to use when you need them.
Using a temporary email involves opening a new tab, Googling for your provider of choice and pasting in the new email. This is too much friction. Burner emails provide you with browser plugins, that give you access to emails that forward to your real inbox directly on the email form. This is faster than even typing in your real email address.