Well, for a start, many of my contacts have multiple phone numbers.
Yeah, OK, I could put them in the SIM multiple times, one for each phone number (with artificially altered names to make them distinct).
Some of my contacts are business contacts and it is important to know what company they are with. Yeah, OK, I could work around that too.
Some of my contacts are f2f contacts and it really is necessary to know their street address.
Of course I have email addresses recorded against many of my contacts, and some of them will have multiple email addresses.
I have even been known to add textual notes and birth dates to my contacts but, yeah, I admit that that is “nice to have”.
In summary, my expectations are for a full function “address book” - and that is well beyond what a SIM can provide.
I mention again … when you migrate from one phone to another, “contacts” is just one small part of it. So even if a SIM could provide a full function “address book” there is still a lot missing. So it is more functional to deal with the whole migration on a phone-to-phone basis rather than via the SIM card. There is also the small problem that if everything is on the SIM, once you move the SIM out of the old phone, you just lost access to all that information on the old phone.
Also, if a customer is more concerned about information security than the average person then there is also the problem that the more you entrust to the SIM, the more you are entrusting to a blackbox computer. So putting everything on the SIM doesn’t sit well with the general thrust of where Purism is going.
However at the end of the day, if the SIM does everything that you want then as it stands today you will need to do a bit of work to read the contacts from the SIM and then do something useful with that information.
It isn’t out-of-the-box today but it can be tomorrow, which is a reason to think that the future is bright. Yes, there are a lot of functional gaps but with time and effort those gaps can be addressed.