Chrome allows installing unsigned extensions by enabling developer mode in chrome://extensions. On browser startup you'll see a warning [1] that encourages you to disable unsigned extensions, but users are offered a choice.
I do trust Mozilla, though I'd prefer if they'd also trust me to be capable of making an informed decision and give me a choice while using their product.
It's not an optimal choice, because Firefox Developer Edition is not based on the latest stable release of Firefox, and because users shouldn't be forced to switch to browsers with an alternative focus just to enjoy Firefox with a local extension.
Permanently installing unpacked or unsigned extensions is a feature that all major browsers offer for their users, except Firefox.
I do trust Mozilla, though I'd prefer if they'd also trust me to be capable of making an informed decision and give me a choice while using their product.
[1] https://i.imgur.com/iGEYMwv.png