AFAIK they're working on it to get it to the same level so you could give official signatures and log into govt services etc using that as well.
You don't need it all the time, only to sign up. Your argument doesn't quite make sense.
All of this is backed by the "single basket" of people actually showing up in the population registry office...
PS: I see, you have just joined HN to write these unsubstantiated comments.
As one example most government procurements over a certain amount od money happen as e-procurements with strict time limits that can't be changed and bids need to be digitally signed. If you can't access digital government services you can neither access e-procurment site nor digitally sign you bid.
If there's no redundancy measure for the ID card system failing - for example, automatically extending deadlines - that's a problem, and an easily solvable one at that, since it's mostly policy. It's not something against the ID card system.
So if a person doesn't already have Mobile-ID and their ID-Card certs are blocked they can't get a Mobile-ID and thus they can't access any digital government services.
It's not like this is purely theoretical - large number of Estonian Id-Card will have their certs blocked and not everyone has Mobile-ID.
2. Mobile-ID requires you to pay for signing up and after that, 1€/month to your mobile provider.