Don’t blame Sparrow. Blame the terrible market for email clients.
I just choose to blame email for being a terrible medium (albeit one I use more than I care to admit) that sucks to write clients for.
I really look forward to the day when email goes away in favor of some kind of trusted-sender-always-encrypted-spam-fighting-ubiquitous system, but given the disparity of systems and needs, and the sheer lack of will to change by the populace-at-large, I doubt we see it anytime soon.
I just choose to...being a terrible medium (albeit one I use more than I care to admit)...