Thunderbird is free software made by volunteers, as such, it doesn't need to fit anywhere in any market. People like it. You don't have to, and that's fine.
For me, I like it because browsers are a huge mess of surveillance and ad targeting--even Firefox. Not to mention the speed. Even on a fast computer, loading a browser, then opening Gmail is not a quick process. By contrast, Thunderbird opens fairly quickly (Not like notepad on a Windows NT device, but for a modern application, it's pretty fast).
Finally, IMAP has been around since 1986, why would you shuffle gigabytes of email across multiple devices? Inb4 you still need to download with imap. I know, but a good IMAP client only downloads the folder you're currently looking at, then syncs it back to the server, no "shuffling" required.
For me, I like it because browsers are a huge mess of surveillance and ad targeting--even Firefox. Not to mention the speed. Even on a fast computer, loading a browser, then opening Gmail is not a quick process. By contrast, Thunderbird opens fairly quickly (Not like notepad on a Windows NT device, but for a modern application, it's pretty fast).
Finally, IMAP has been around since 1986, why would you shuffle gigabytes of email across multiple devices? Inb4 you still need to download with imap. I know, but a good IMAP client only downloads the folder you're currently looking at, then syncs it back to the server, no "shuffling" required.