"I use Thunderbird because ______"
@thunderbird HOW FUNNY THAT THE WORD "PRIVACY" MATCHES THE MISSING WORD....
...
Privacy?

Because it is free as in "free speech"

@thunderbird
I like it, it's FOSS, and it's available as a Flatpak
Oh and it's not built on "web technologies"
@thunderbird I use Thunderbird because it can, with great effort, be used as a replacement for fetchmail...
https://personal.cis.strath.ac.uk/william.waites/misc/orifice365/
@thunderbird
... I need an e-mail client.
(And not rubbish.)