Why shouldn't they? The burden to demonstrate a compelling argument should always be on those who want to restrict freedom, not on those who want to enjoy (or retain) freedom.

We're talking about restricting the freedom of a corporation to increase the freedom of people. So, as you stated, why should the status quo exist and restrict the freedom of consumers?

The people's freedom is not restricted by Apple deciding to include or exclude certain features from their phones.

If people don't like the phones, they don't have to engage with the ecosystem at all. Many diehard anti-Apple (or anti-smartphone-in-general) people do just this today.

You also have this freedom if you don't like Apple products.

I, for example, have just purchased my last iPhone.

It's not certain features. It's an app store that determines what software you can run on the hardware you already purchased, even retroactively disabling it. This is on top of their continued intensive efforts to thwart repairs of the hardware itself outside of Apple.

Plenty of corporations and corporate actions are regulated even when the consumer has choice. Because choice alone is not the issue, and that's usually with options that have far more than 2 ecosystems.

Because it has become a democrat vs republican kind of choice in all practicality.

I think there's a difference between regulations controlling externalities, or protecting the dispossessed, and protecting people from phones that don't have certain games. Do you not?

No, because the regulation isn't protecting people from phones that don't have certain games. That would be silly.

Allowing over a billion users the freedom to install and use software on their smartphone (a critical computing device and the only one for many) without corporate approval can indeed control externalities, protect the dispossessed and even save lives.