As someone who built a SaaS for your 2nd use case (Homechart: https://homechart.app https://homechart.app, lifetime license available!), the real reason is any

As someone who built a SaaS for your 2nd use case (Homechart: https://homechart.app https://homechart.app, lifetime license available!), the real reason is any kind of software that integrates with other things has an ongoing maintenance cost that needs to be paid by all of the users to keep it working. Like connecting to your bank accounts, that's not a one and done thing typically.