What is preventing manufacturers from removing the SIM card?

[rui no onna]

And if you want it so it's SIMless and all you have to do is use software to switch carriers better be ready to lobby Congress for new laws.

Telecoms have more money for lobbyists.

Additional concerns:

What/where will be the central exchange for carrier selection? Apple? In the US, the embedded SIM card on iPads only lets you choose from a few carriers right now. No option for Cricket, Straight Talk, etc.

If you travel to a different country, can you choose a local carrier for cheaper rates instead of being forced on roaming? Last time I traveled to the Philippines, the local carriers there weren't supported via Apple SIM/embedded SIM. My only option via embedded SIM was roaming or GigSky which was significantly more expensive compared to local rates. Happy to have an available SIM card slot so I can just pop in a local SIM (available for purchase from any convenience store for $2).
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Not since the introduction of Mobile Virtual Network Operators (MVNO) like Google Project Fi.

The distribution of SIMs is costly and time consuming. There are very few reasons to keep them around.

MVNOs have been around for a long time.

The Sprint and Verizon CDMA based MVNOs, used to be your only option for cellphones are cheap flip phones and candy bars that you can't use with any other carrier. It took a heck of a long time and workarounds before you can get smartphones on CDMA MVNOs.

The AT&T and T-Mobile GSM based MVNOs? If you can get an unlocked phone from overseas supporting the requisite bands, just pop a SIM card and go.

Maybe eSIM might work for Europe. In the US, it would probably just give more control to the carriers.

 

[Applejuiced]

Telecoms have more money for lobbyists.

Additional concerns:

What/where will be the central exchange for carrier selection? Apple? In the US, the embedded SIM card on iPads only lets you choose from a few carriers right now. No option for Cricket, Straight Talk, etc.

If you travel to a different country, can you choose a local carrier for cheaper rates instead of being forced on roaming? Last time I traveled to the Philippines, the local carriers there weren't supported via Apple SIM/embedded SIM. My only option via embedded SIM was roaming or GigSky which was significantly more expensive compared to local rates. Happy to have an available SIM card slot so I can just pop in a local SIM (available for purchase from any convenience store for $2).

Exactly.
It's a whole new infrastructure that would need to be build and then wireless carriers and device manufacturers will fight for who controls it.
And in many countries that don't support such new embedded sim and many smaller carriers that do not either will be left out.
The one who loses in the end is the consumer having less options and a tighter control of their device by others.