Jetbrains can offer a perpetual license[1] in theory because old versions don't continue getting updates. They spend (relatively) little on "supporting" old versions -- mostly just the cost of the download servers.
The two use cases you described don't work that way. Both of them have cloud components, which means they need frequent security patches, and they likely also need bug fixes and other updates.
"Connects to my different accounts" by itself is a huge undertaking that most people outsource to Plaid or a similar vendor.
So to answer your question: a lot (not all, but most) SaaS products are services because they are services. They are updated incessantly by developers and have rolling updates.
To me, the keep your old version forever was a thing Jetbrain did to "soften" the blow when going from buy once, use forever.. to buy every single month.
Still, one of the most valuable softwares I pay for.
A lot of people really didn't like the fact they were going from having a perpetual license to having a subscription. The reality is, the way it worked out is basically the same as before but I could pay monthly. Since I paid for my own license instead of allowing an employer to buy it (so I could get IntelliJ for all languages instead of getting a language specific version) that was nicer.
The two use cases you described don't work that way. Both of them have cloud components, which means they need frequent security patches, and they likely also need bug fixes and other updates.
"Connects to my different accounts" by itself is a huge undertaking that most people outsource to Plaid or a similar vendor.
So to answer your question: a lot (not all, but most) SaaS products are services because they are services. They are updated incessantly by developers and have rolling updates.
1. https://sales.jetbrains.com/hc/en-gb/articles/207240845-What...