I've had an e-mail address since 1999 or so, back when usa.net was still a thing. Until about this time last year, I was strictly a webmail reader. Never saw the point in configuring Outlook/Eudora/Thunderbird/Geary, etc. HTML email inside my browser worked just fine, and it meant I could check it from any computer, to boot.
Then I read some story on HN about a guy getting his gmail account shutdown and subsequently losing access to his emails, his Drive, his Photos, several websites he had hosted through Blogger, etc. And since these were all "free" services provided by Google, when they decided to shut down his account, he had no legal recourse.
The idea of losing 10+ years of emails at the whim of my provider didn't sit well with me, so at that point I installed Thunderbird on my desktop and started keeping a local copy of all my e-mails. Just in case.