Do you have any devices on your local network where the firmware hasn't been updated in the last 12 month? The answer to that is surprisingly frequently yes, because "smart device" companies are laughably bad about device security. My intercom runs some ancient Linux kernel, my frigging washing machine could be connected to WiFi and the box that controls my roller shutters hasn't gotten an update sind 2018.
Not everyone has those and one could isolate those in VLANs and use other measures, but in this day and age "my local home network is 100% secure" is far from a safe assumption.
Heck, even your router might be vulnerable...
Adding HTTPS is just another layer in your defense in depth. How many layers you are willing to put up with is up to you, but it's definitely not overkill.