I wouldn't call them outlandish. I think there's merit in the ability to install whatever software you want. But I also think there's merit in making sure there's a robust, unfragmented market of apps that work with the last 6 years of iPhones, and restrictions that Apple has in place ensure that.
I think the Dev Store is a reasonable compromise to ensure that average users don't have to run AVG AntiVirus on their phones. That situation is absurdly anti-user.
>why is there no strict walled garden for Macs?
There is, and it's annoying: GateKeeper, which if I recall correctly requires you to basically outsmart your OS to install software using the GUI.
This is why I'm happy the iPad Pro is getting more desktop-like, hopefully bridging the gap between people who want a laptop to do weird stuff and people who want a device that will work no matter what you do to it.