You need to keep in mind that carriers have near-zero actual engineering capability. They're a marketing & financing operation with a very small technical skeleton crew, with most of the actual network management outsourced to their equipment vendor.
5G is relatively "simple" to support - you give a ton of money to your equipment vendor, they give you new equipment to install and it's done. The vendor happily does all the work for a fee and they can do it fine because it's not their first rodeo.
eSIM on the other hand ties into the account & billing management software which is custom for each carrier (and it's a "big ball of mud" of crappy Java accumulated over 2 decades). The vendor can't help here - each carrier has their own ball of mud, so there is no economies of scale possible here.
5G is completely transparent to the "big ball of mud". The differing bits are all handled by the vendor-provided equipment, the ball of mud doesn't know/care. 5G doesn't change any fundamentals - the big ball of mud can treat it as a 2G network. You've still got phone numbers, CDRs, etc.
eSIM is a fundamental change though. You go from physical SIMs that must be created & registered in advance, and then linked to an account by some privileged user (CS agent or in-store employee), to "SIMs" that can be created out of thin air and registered by the user themselves. This requires new functionality in the "big ball of mud". The security profile also changes - with physical SIMs the security is provided by the privileged user who is supposed to check the legitimacy of any SIM swap/registration request. With eSIMs this is done online by the user, so there needs to be additional security checks, fraud protection, etc that the existing system (which so far was pretty low stakes as no security-critical action could be done online) suddenly needs to be hardened to support.
This would be no big deal for a dedicated engineering team at any decent tech company or even startup, but these companies are as far away from "tech/startup" as you can imagine, and no competent engineer would want to work there for the terrible pay/conditions/pervasive mediocrity that's in such companies. It's the same situation as with legacy banks still not being able to catch up to the functionality & user experience offered by modern "challenger banks" despite having orders of magnitude more resources and capital.
How about MVNOs and eSIMs? Is this something where MVNOs might have an easier time since they're smaller/newer companies than the big incumbents? I've only done the travel eSIM thing once, but it seemed like they were using small MVNOs rather than any big carriers when I visited North America this way.
It depends if they're building new towers or just upgrading existing ones. Doing a like-for-like swap can presumably be done entirely by the vendor, setting up new sites indeed needs a bit of work, so maybe whatever little technical staff they have handles that (or maybe even that is outsourced too).
> How about MVNOs and eSIMs?
When it comes to MVNOs it depends whether the MVNO runs (at least parts of) their own infrastructure or is just white-labelling the upstream carrier's one.
In the former case they can indeed do it, but the company culture challenges still apply. You need to hire and retain good engineers, something I'm not aware of any telecom company actually prioritizing. Meaning they too will eventually end up with a ball of mud in a few years.
In the latter case they're just reselling the upstream turd with a bit of polish. If the upstream ball of mud can't manage eSIMs, they can't either.
> I've only done the travel eSIM thing
I wouldn't recommend relying on these. You're getting bottom-of-the-barrel capacity that (even if it works) is so slow that you'd be lucky to even use up half your data cap. You are always roaming and your data is tunnelled through what feels like some dial-up modem in some shady warehouse. These are a scam.
I've used them quite a lot around Europe and once or twice in Africa (and even locally, when I didn't have an unlimited data plan and used all of my allotted data by my carrier and it was easier to just buy an eSIM), and my experience has always been pretty good.
Note that I am talking about these Airalo, Nomad, etc eSIMs sold online, not eSIMs sold directly by the carrier themselves (the latter would generally be as good as the carrier's own prepaid offering).
>I've tried a few of these and can rarely pull more than a few megabits per second (in a location where a carrier's own SIM pulls 150+).
That seems.. fine? If you're traveling and your use case is checking google maps, or logging into airbnb to pull up your booking, you don't need 150 Mb/s of speed and low latency. The only case where it might be dodgy is if you're doing voip calls or watching streaming videos, but why are you doing those things on vacation? Sure, it'd be nice to have a local sim with low latency and high speeds, that's often much more expensive than esims and/or comes with more hassle (eg. KYC or having to pick up the sim in-person).
The esim thing is a little curious though, because it seems like that should be pretty easy for carriers to support, unlike for instance only supporting 5G. Maybe there's something I don't understand about esim implementation at the carrier level.
As an aside, though, esim is really a godsend when traveling. Instead of having to get a local SIM card somewhere and get that set up, there's a bunch of easy-to-use services where you just install an app on your phone and buy a temporary-use esim while you're traveling in a particular country. You can buy the esim beforehand, and then switch to it when your plane lands.